We know that the process by which Ireland was peopled was many layered. This is also the assumption of its origin story, Lebor Gabála Érenn (the Book of Invasions).
Here are my raw and speculative conjectures on how this originally oral tradition of legendary history might be connected to reality:
* The Fomorians may have been the Mesolithic hunter-gatherer people of Ireland. They were by tradition a seafaring people and in some traditions arrived from North Africa both of which would be consistent with what we know of the Atlantic Mesolithic people who left traces such as mtDNA V from North Africa to Arctic Saami people of Finland. There were only a few thousand European hunter-gatherers in Ireland prior to the Neolithic revolution.
By tradition they were the first people in Ireland after Noah's flood before the Partholón and only after the Cessair (discussed below). Western European hunter gathers persisted in Ireland past the fall of the first farmers for about 6,000 years, and would have been racially much more distinctive than later waves of invaders would have been from each other which could account for their physical descriptions as rather grotesque despite the fact that they can produce children with the invaders.
Incidentally, while Ireland was not depopulated by a flood, it was completely depopulated for thousands of years from about 28,000 BCE to 15,000 BCE when it was covered by ice sheets (a frozen flood for those who would like to stretch for a literal correspondence) and then not immediately repopulated when the ice sheets retreated.
* The Partholón may have been the first farmers of Ireland descended from the Cardial Pottery wave of the Neolithic Revolution and arriving via Iberia ca. 4500 BCE whose demise in the story corresponds to the collapse of the first wave farmers of Ireland about ca. 3300 BCE from a peak population ca. 3700 BCE of about 100,000-200,000 people. Their legendary route, by sea from Anatolia to Greece to Sicily to Iberia isn't far from the Cardial Pottery route.
The proprietor of the Old European Culture blog would associate this wave with the first metal age arrivals many centuries later, as they reputedly bring gold to Ireland, but I would note that they do not necessarily more practical metals and that panned gold has a tradition of being retrieved from Caucasian springs since very ancient times and takes less skill to extract than copper or tin. Still, he has a point. Gold was a distinctive feature of Bronze Age Ireland and was rare before then. But, first wave Neolithic people in Ireland, like the Partholón, was a civilization that collapses before subsequent invaders arrived, while Bell Beaker culture was conquered without collapsing in Ireland, and had origins in Anatolia but not in the steppe.
* The Nemed may have been the first Bell Beaker People to arrive in Ireland, by tradition, from the Caspian Sea who clash with the Formorians in multiple battles, and then leave for "the north of the world", for Britain and for Greece. The Greek branch, the Fir Blog return to Ireland after a couple of centuries, and nine of their successive kings rule Ireland for the next 37 years. Their successors, the Tuatha Dé Danann are also descendants of the Nemed, in particular, those who went "into the north of the world" who wrest Ireland from their kin the Fir Bolg and rule another 150 years. In real life, the Bell Beaker people arrive in Ireland around 2500-2200 BCE, but it wouldn't be at all surprising if the continent-wide Bell Beaker civilization, which I've speculated may also have links to the Greek Minoans (like the Fir Blog), comprised factions within themselves who waxed and waned in the Irish political sphere over a period of fifteen centuries or more, about a factor of ten longer than in the story. The Fir Blog are also said in legendary history to be contemporaneous with the Israelite Exodus, which would be about right in this chronology.
* The Milesians, finally, would represent the Celtic speaking Gaels, who arrive in Ireland in reality sometime between the 9th and 4th centuries BCE, quite possibly from Iberia as tradition suggests. This transition, historically, as in the myth, may have been comparatively peaceful reaching a treaty after an early spat of fighting. The association of the Tuatha Dé with the underworld may reference not only their sídhe burial mound practices (in contrast to Indo-European cremation), but also their background as miners of metal from the ground.
This analysis doesn't leave a place for the first wave of invaders, the Cessair, who are descended from Scythians, which would be a likely place of origins for the ancestors of the proto-Celts. This story appears to be derived from the history of the Gaels in the History of the Franks origin story, and the History of the History of Britain's origin story likewise associates this story with the Gaels. Also, notably, these people do not encounter the Fomorians whom later waves of Irish invaders do encounter, and provides origin stories that could plausibly be for all of the people of the world, or at least, all of the Indo-European peoples. This story, therefore, may be out of order and actually represent the prehistory of the Milesians Gaels before their arrival in Ireland, rather than the true first wave of invaders of Ireland.
This analysis gives both populations with genetic steppe origins - the Bell Beakers and the Celts, a steppe origin in legendary history, while denying it to each of the populations which probably didn't have a steppe origin but did expand out of Anatolia as in legendary history.
Wednesday, December 30, 2015
Tuesday, December 29, 2015
An Interesting Etymology Of "Open Sesame" In Ali Baba And The Forty Thieves
It turns out that the story of Ali Baba and the Forty Thieves was a late addition to the 1001 Nights Anthology of stories probably added from oral tradition received in Syria by a Frenchman who is the first person to have put it in print, centuries after the other stories were written down.
And, the code word "Open Sesame" in the story, perfectly corresponds to the Serbian phase "otvori se za me" meaning "open yourself for me.", which is just what the magical stones do when prompted by the code word.
But, what is a Serbian phase doing in an Arabian story?
Well, it turns out the Slavs were relocated by the Byzantines to serve as buffer populations between them and the Islamic Ottoman empire right along the Syrian border. So it is natural that a Serbian story might make its way into an orally transmitted tale in Syria.
Via the Old European culture blog (indeed, "Baba" also has plausible Slavic etymologies consistent with the poor woodcutter of that name in the story, as explored in later posts at the same blog).
And, the code word "Open Sesame" in the story, perfectly corresponds to the Serbian phase "otvori se za me" meaning "open yourself for me.", which is just what the magical stones do when prompted by the code word.
But, what is a Serbian phase doing in an Arabian story?
Well, it turns out the Slavs were relocated by the Byzantines to serve as buffer populations between them and the Islamic Ottoman empire right along the Syrian border. So it is natural that a Serbian story might make its way into an orally transmitted tale in Syria.
Via the Old European culture blog (indeed, "Baba" also has plausible Slavic etymologies consistent with the poor woodcutter of that name in the story, as explored in later posts at the same blog).
Time Window Of Transition From First Farmer To Steppe Ancestry In Ireland Narrowed
As I've suspected since at least about four year ago, the modern Western European genetic profile, with lots of Y-DNA R-1b, lactase persistence, and steppe-like autosomal ancestry is a package that arrived sometime after the first wave Neolithic farmers of the megalithic culture and was in place by the Bronze Age in Western Europe, with the Bell Beaker People (whose own linguistic affiliation and origins are somewhat cryptic).
Both Paleolithic continuity theories and Neolithic continuity theories for the source of the modern Western European genotype are now basically ruled out by the ancient DNA.
The window of time in which this happened is narrowed to roughly 3000 BCE to 2000 BCE, i.e. Chalcolithic or early Bronze Age, and probably coincides with about 2500 BCE in Ireland when the Chalcolithic age began and Bell Beaker people appeared.
The Chalcolithic people were able to have such a large demographic impact because farming after thriving in Ireland from ca. 3700 BCE to 3400 BCE, then basically collapsed with farmers reverting to hunting and gathering for much of their sustenance.
As usual, I am skeptical that the wave of migration that brought this demographic transformation was in fact Indo-European Celtic, as obvious an assumption as that might seem, as opposed to a scenario in which the genetic shift is associated with a Bell Beaker linguistically Vasconic population and the language shift from a Vasconic substrate to Celtic occurs later ca. 1200 BCE around the time of Bronze Age collapse.
Eurogenes posts the results without original post comment, but there is lots of discussion in the comments to the post.
According to Bernard's post, the Y-DNA type for all three men was (to the extent of commonality): R1b1a2a1a2c aka R1b-L21, the most common Y-DNA type in the British Isles today, and a sister clade of the Yamnaya Y-DNA R1b haplogroup.
He notes (in French):
Dienekes' Anthropology Blog notes from the body text of the article the following ancestry proportions in the Bronze Age sample:
Previous studies have shown an affinity to Iberian genetics in the British Isles and I haven't had time to read this closely enough to determine if these studies affirm that conclusion. On the other hand, intriguing cultural and linguistic clues seem to connect the Balkans and Ireland, although the direction of transmission is not obvious.
In the PCA chart from the paper, the Hungary and German Late Neolithic and Bronze Age individuals are closer to the Irish samples than the Spanish Chalcolithic samples, which are at the Neolithic farmer side of an axis that has German Corded Ware and Steppe individuals at the other end of the axis.
Razib has meaty coverage with lots of context and analysis, most of which I tend to agree with (he does not directly engage with the linguistic question). He notes the relevance of legendary history which shouldn't be taken literally but provides useful information. He provides the general context which is familiar to most of my readers. Particularly noteworthy is this little bit of insight:
But, I also continue to think that the Bell Beaker people were not Proto-Celtic IE people, despite the trend in most of the 20th century's anthropology to think of Bell Beaker is something other than a folk migration, and that instead there was a subsequent language shift around the time of Bronze Age collapse with much less demic impact. Mostly this is because I don't think that Basque people who exemplify the Western European Chalcolithic source were ever proto-Celtic speakers and because of the Vasconic substrate in place names in Western Europe and the thousand year division between Bell Beaker derived territory and Corded Ware territory culturally.
I do think that the geographic range of Celtic closely tracks places that had a Vasconic substrate, however, and is distinct as an IE language family largely due to that substrate influence. It isn't impossible to imagine that the Bell Beaker people were linguistically Vasconic, and I do think that the language of the first farmers was probably closer to Vasconic than IE was, but I don't think that the megalithic first farmer language survived anywhere (except perhaps on a few Mediterranean islands like Sardinia) into historically attested times.
In other Bell Beaker news, Bell Beaker mtDNA is closer to Minoan mtDNA than to somewhat similar Androvo and Unitice mtDNA. Rossen mtDNA is considerably more dissimilar. This follows suggestive evidence from Y-DNA and other sources of Minoan-Bell Beaker similarity, although neither case has really been conclusive.
I suspect that the Minoans were part of the Aegean wave of an Anatolian demic transition between first farmers and early metal age farmers. Even if they weren't directly ancestral to the Bell Beaker people, they probably had common origins and quite possible belonged to the same language family.
Both Paleolithic continuity theories and Neolithic continuity theories for the source of the modern Western European genotype are now basically ruled out by the ancient DNA.
The window of time in which this happened is narrowed to roughly 3000 BCE to 2000 BCE, i.e. Chalcolithic or early Bronze Age, and probably coincides with about 2500 BCE in Ireland when the Chalcolithic age began and Bell Beaker people appeared.
The Chalcolithic people were able to have such a large demographic impact because farming after thriving in Ireland from ca. 3700 BCE to 3400 BCE, then basically collapsed with farmers reverting to hunting and gathering for much of their sustenance.
As usual, I am skeptical that the wave of migration that brought this demographic transformation was in fact Indo-European Celtic, as obvious an assumption as that might seem, as opposed to a scenario in which the genetic shift is associated with a Bell Beaker linguistically Vasconic population and the language shift from a Vasconic substrate to Celtic occurs later ca. 1200 BCE around the time of Bronze Age collapse.
The Neolithic and Bronze Age transitions were profound cultural shifts catalyzed in parts of Europe by migrations, first of early farmers from the Near East and then Bronze Age herders from the Pontic Steppe. However, a decades-long, unresolved controversy is whether population change or cultural adoption occurred at the Atlantic edge, within the British Isles. We address this issue by using the first whole genome data from prehistoric Irish individuals.
A Neolithic woman (3343–3020 cal BC) from a megalithic burial (10.3× coverage) possessed a genome of predominantly Near Eastern origin. She had some hunter–gatherer ancestry but belonged to a population of large effective size, suggesting a substantial influx of early farmers to the island.
Three Bronze Age individuals from Rathlin Island (2026–1534 cal BC), including one high coverage (10.5×) genome, showed substantial Steppe genetic heritage indicating that the European population upheavals of the third millennium manifested all of the way from southern Siberia to the western ocean. This turnover invites the possibility of accompanying introduction of Indo-European, perhaps early Celtic, language.
Lara M. Cassidy, Rui Martiniano et al. "Neolithic and Bronze Age migration to Ireland and establishment of the insular Atlantic genome" PNAS (2015) (paragraph breaks and emphasis mine).Irish Bronze Age haplotypic similarity is strongest within modern Irish, Scottish, and Welsh populations, and several important genetic variants that today show maximal or very high frequencies in Ireland appear at this horizon. These include those coding for lactase persistence, blue eye color, Y chromosome R1b haplotypes, and the hemochromatosis C282Y allele; to our knowledge, the first detection of a known Mendelian disease variant in prehistory. These findings together suggest the establishment of central attributes of the Irish genome 4,000 y ago.
Eurogenes posts the results without original post comment, but there is lots of discussion in the comments to the post.
According to Bernard's post, the Y-DNA type for all three men was (to the extent of commonality): R1b1a2a1a2c aka R1b-L21, the most common Y-DNA type in the British Isles today, and a sister clade of the Yamnaya Y-DNA R1b haplogroup.
He notes (in French):
Ils appartiennent à l'haplogroupe du chromosome Y: R1b-L21. Cet haplogroupe est fréquent aujourd'hui dans les Îles Britanniques. On a retrouvé son haplogroupe "père" R1b-P312 dans tous les squelettes campaniformes d'Europe Centrale et son haplogroupe "oncle" R1b-Z2103 dans la plupart des squelettes de la culture Yamnaya dans les Steppes Pontiques. Ces haplogroupes sont absents chez les squelettes des chasseurs-cueilleurs et des fermiers Néolithiques d'Europe.The mtDNA profile of the three Bronze Age individuals, two of which have mtDNA U5a, suggests that the Bronze Age impact may have been male dominated with Bell Beaker men marrying local women many of whom had hunter-gatherer matriline ancestors.
Dienekes' Anthropology Blog notes from the body text of the article the following ancestry proportions in the Bronze Age sample:
Typically of Middle Neolithic individuals, the Irish Neolithic sample is enriched in hunter-gatherer ancestry relative to early Neolithic individual, probably indicating a resurgence of local relict hunter-gatherer populations, whose status increased and facilitated introgression, when farming was temporarily discredit after the failure of the first wave of farming in Ireland. But, she had no steppe ancestry. The ancestry percentages aren't inconsistent with a near total replacement of Bronze Age men with proportionately fewer migrating Bell Beaker women.Linearbandkeramik (Early Neolithic; 35 ± 6%), Loschbour (WHG; 26 ± 12%), and Yamnaya (39 ± 8%), in the total Irish Bronze Age group. These three approaches give an overlapping estimate of ∼32% Yamnaya ancestry.
Previous studies have shown an affinity to Iberian genetics in the British Isles and I haven't had time to read this closely enough to determine if these studies affirm that conclusion. On the other hand, intriguing cultural and linguistic clues seem to connect the Balkans and Ireland, although the direction of transmission is not obvious.
In the PCA chart from the paper, the Hungary and German Late Neolithic and Bronze Age individuals are closer to the Irish samples than the Spanish Chalcolithic samples, which are at the Neolithic farmer side of an axis that has German Corded Ware and Steppe individuals at the other end of the axis.
Razib has meaty coverage with lots of context and analysis, most of which I tend to agree with (he does not directly engage with the linguistic question). He notes the relevance of legendary history which shouldn't be taken literally but provides useful information. He provides the general context which is familiar to most of my readers. Particularly noteworthy is this little bit of insight:
But some inferences can be made with various techniques, the details for which you should read the supplements. The Neolithic female seems to be descended from Cardial, and not LBK, early European farmers. That is, the Irish Neolithic is connected to the Atlantic littoral, in keeping with Barry Cunliffe’s thesis in Facing the Ocean. Second, the excess hunter-gatherer ancestry in the Neolithic female exhibits greater affinities with the Loschbour hunter-gatherer from Luxembourg than hunter-gatherers from Central or Eastern Europe. This indicates that as with the the situation in Spain there was local admixture with hunter-gatherers over time.From off topic comments on this paper to another of my posts at this blog form Nirjhar007 on December 28, 2015:
Naturally this leads one to wonder if the early European farmer ancestry in the Bronze Age Irish samples was from the same group as that of the Neolithic farmer. The surprise is that there isn’t any strong evidence of admixture! Rather, there are better candidates for donor populations on the European continent. The most parsimonious explanation then is that the Bell Beakers mixed with early European farmers, and then rolled over the descendants of the Megalith builders in Ireland. But confidence in this sort of conclusion is weak, as the number of populations is finite, and one should be cautious about making too many inferences from a few samples (though modern Irish are actually a decent proxy for the Bronze Age Irish).
Do you think its too early for that R1b to be IE?Yes.
Do you this goes along with this?
Metallurgy arrived in Ireland with new people, generally known as the Bell Beaker People, from their characteristic pottery, in the shape of an inverted bell.[9] This was quite different from the finely made, round-bottomed pottery of the Neolithic. It is found, for example, at Ross Island, and associated with copper-mining there. It is thought by some scholars to be associated with the first appearance of Indo-Europeans in Europe (possibly Proto-Celtic),[10] though this theory is not universally accepted.
I think it is increasingly undeniable that the Chalcolithic demic change in Western Europe was due to the Bell Beaker People.The Bronze Age began once copper was alloyed with tin to produce true Bronze artefacts, and this took place around 2000 BC, when some Ballybeg flat axes and associated metalwork were produced. The period preceding this, in which Lough Ravel and most Ballybeg axes were produced, and which is known as the Copper Age or Chalcolithic, commenced about 2500 BC.
But, I also continue to think that the Bell Beaker people were not Proto-Celtic IE people, despite the trend in most of the 20th century's anthropology to think of Bell Beaker is something other than a folk migration, and that instead there was a subsequent language shift around the time of Bronze Age collapse with much less demic impact. Mostly this is because I don't think that Basque people who exemplify the Western European Chalcolithic source were ever proto-Celtic speakers and because of the Vasconic substrate in place names in Western Europe and the thousand year division between Bell Beaker derived territory and Corded Ware territory culturally.
I do think that the geographic range of Celtic closely tracks places that had a Vasconic substrate, however, and is distinct as an IE language family largely due to that substrate influence. It isn't impossible to imagine that the Bell Beaker people were linguistically Vasconic, and I do think that the language of the first farmers was probably closer to Vasconic than IE was, but I don't think that the megalithic first farmer language survived anywhere (except perhaps on a few Mediterranean islands like Sardinia) into historically attested times.
In other Bell Beaker news, Bell Beaker mtDNA is closer to Minoan mtDNA than to somewhat similar Androvo and Unitice mtDNA. Rossen mtDNA is considerably more dissimilar. This follows suggestive evidence from Y-DNA and other sources of Minoan-Bell Beaker similarity, although neither case has really been conclusive.
I suspect that the Minoans were part of the Aegean wave of an Anatolian demic transition between first farmers and early metal age farmers. Even if they weren't directly ancestral to the Bell Beaker people, they probably had common origins and quite possible belonged to the same language family.
Sunday, December 27, 2015
Non-Commutative Geometry Could Be Key To Quantum Gravity
Marco Frasca argues suggestively that the path to quantum gravity involves non-commutative geometry, a field that one of my most promising fellow students from college pursues professionally.
Should We Be Skeptical Of The 750 GeV Bump?
Jester points out some likely logical corollaries in terms of expected experimental output if the 750 GeV bump is real which have not obviously manifested yet.
Updated December 29, 2015:
Matt Strassler engages in a similar exercise in a somewhat more accessible manner. He starts by making clear that it couldn't be a Higgs boson, because if it produced that many diphoton events (which is can't produce directly since photons only couple to charged particles and this is electrically neutral) it would produce far too many top-antitop quark or tau-antitau pairs to escape notice at the LHC until now.
So, there needs to be some new undiscovered intermediary particle.
Updated December 29, 2015:
Matt Strassler engages in a similar exercise in a somewhat more accessible manner. He starts by making clear that it couldn't be a Higgs boson, because if it produced that many diphoton events (which is can't produce directly since photons only couple to charged particles and this is electrically neutral) it would produce far too many top-antitop quark or tau-antitau pairs to escape notice at the LHC until now.
So, there needs to be some new undiscovered intermediary particle.
If this bump is a real particle, there must be at least one other particle that makes such a two-photon bump possible. That new particle (maybe heavy, or maybe lightweight) hasn’t yet been found by the ATLAS or CMS (or LHCb!) experiments, but is almost certainly accessible to them. In fact, signs of an additional particle or particles may already be obvious (or almost obvious) in their existing data. It might just be a question of looking in the right place and of asking the right question. . . .Of course, the lack of a theoretically well motivated particle that could produce the 750 GeV diphoton excess is one reason that many people think that this might simply be a false alarm and statistical fluke.
There are a lot of possibilities. It could be a simple elementary particle like the electron, interacting with known particles indirectly, as a result of direct interactions with some heavy, as yet unknown particles. It could be a composite object like a proton, made from objects bound together by a new force that we are about to discover. It might be that the photons to which it seems to decay aren’t photons after all, but are new particles that mimic photons in some way (an idea that goes back at least to 2000.) I certainly don’t know what it is, and neither does anyone else yet. But each of the many different ideas comes with predictions — predictions which in many cases lead to LHC signals that can be looked for NOW!
Sunday, December 20, 2015
Modifications To Gravity Continue To Look Attractive Relative To Dark Matter
One of the ongoing debates in modern physics is between the dark matter hypothesis and the hypothesis that phenomena attributed to dark matter is actually a result of us using inaccurate laws of gravity that require modification.
* At the beginning of this year, I provided my predictions for this area and recapped the status of the research. Then, I said:
* A good place to start the discussion, however, is with a 2014 summary of the state of warm dark matter and cold dark matter models:
SIDM models, because they introduce a new force and not just a new particle, also fair less well in Occam's Razor relative to gravity modification models, than simple singlet dark matter models that struggle mightily to be reconciled with empirical data, for which the consensus is that the answer is "warm dark matter or bust."
A year later, Brooks is co-author of an article that compares CDM to SIDM in simulations with baryonic matter feedback and finds that the differences are surprisingly modest.
This past November, Brooks noted that baryonic feedback can help to partially explain the surprisingly number of bulgeless galaxies that are observed, but still struggles to reproduce the relative number of bulgeless and bulgeful galaxies which are observed in real life. Stating that:
* At the beginning of this year, I provided my predictions for this area and recapped the status of the research. Then, I said:
The hunt for dark matter will continue, probably inconclusively as it did in 2014, in 2015. Fundamentally, the problem is that the interpretation of any signals or dark matter exclusions is highly model dependent, and we don't know enough about background processes intergalactic space or even in our own Sun's nuclear dynamics and atmospheric physics, to rule out non-dark matter alternatives to observational results.* A year later, the evidence in favor of gravity modification is strengthening, while the dark matter hypothesis continues to be problematic. I don't have time to do a full fledged analysis of the issue (a did a better one in honor of the 100th anniversary of General Relativity a while ago), but do summarize below some of the notable research on the topic that has taken place in 2015.
Particularly notable will be the extent to which claims of cold dark matter theorists that feedback effects from baryonic matter can solve that theory's failure to reproduce a universe like the one observed can be convincingly supported without self-interacting dark matter. I expect that they will fail. Another worry in the cold dark matter camp is that the Bullet Cluster data is incompatible with many versions of this theory. Cold dark matter proponents may start to migrate into the warm dark matter camp at the margins.
Warm dark matter theorists, in contrast, face renewed arguments that the narrow parameter space of this theory is over constrained by Lyman alpha data and other data points, but proponents will ignore or theorize around this limitations.
DAMA is claiming a seasonal direct dark matter detection signal in the warm dark matter mass range in a late December pre-print, but I suspect that upon further inspection, this will turn out to be merely seasonal variation in the solar neutrino background. DAMA has cried wolf before and been disproved by LUX and others.
It also remains to be seen if the 3.5 keV X-ray signal touted this year, which could be a warm dark matter annihilation signal, will really turn out to be something more than emissions of potassium atoms as the "banana camp" has argued. I suspect that either the banana camp will ultimately win this argument, or that the signal will ultimately prove to be too inconsistent across different galaxies to fit a dark matter annihilation interpretation. Fortunately for warm dark matter proponents, the loss of this piece of evidence is not fatal to warm dark matter in general, since its annihilation properties are model dependent.
Modified gravity proponents have marshaled some arguments such as those related to the tightness of fit of galactic rotation curves to MOND predictions with a couple of minor well reasoned adjustments that are inconsistent with both of those theories. But, the leading MOND theory itself, of course, has always underestimated dark matter in galactic clusters and is missing a theoretically well motivated mechanism. Notably, MOND does particularly poorly in the case of non-spherical galactic clusters. And, it can't explain the Bullet cluster.
I am currently inclined to believe that Deur is right in attributing all dark matter phenomena and much or all of dark energy phenomena to non-linear self-interactions of canonical spin-2 gravitons, and that general relativity theorists have failed to correctly model the self-interaction terms of gravitional fields (a quantum gravity analysis using analogies to QCD highlights this conclusions although it isn't an inherently quantum gravitational observation and could be reproduced in a less transparent way with classical GR equations). If Deur is right, we have already discovered all particles that exist except the graviton and all forces that exist. Basically, GR math has had the right basic axioms, but not quite the right mathematical implementation in complex non-spherically symmetric cases, for a century. But, I don't think that this will gain wide acceptance or even recognition in 2015. Certainly, some researchers disagree (and here). Correspondence with Deur indicates that he has limited resources in the next year to devote to this not part of the day job project, and there isn't yet a critical mass of investigators coordinated in investigating this class of non-linear evaluations of GR axioms with gravitons. Others have also noted the critical role that assumptions other than spherical symmetry have on the non-linear effects in GR.
A scalar theory of gravity with a coupling dependent upon the tightness of matter-clustering produces similar results for similar reasons. Others also note that only mild modifications to GR are necessary to eliminate the need for dark matter.
In general, there is not a strong consensus on the way that the non-linear aspects of GR play out in all but the simplest matter distributions. There are strong suggestions that important, but largely unmodeled configurations like the multi-level cellular structure that seems to characterize the actual distribution of matter in the universe, can amplify these non-linear effects to orders of magnitude sufficient to account for a material share of dark matter and dark energy phenomena (see also here arguing that slight inhomogenities in matter-energy density in the radiation density can replicate the effect of dark matter in the lamda CDM model).
Moffat's MOG theory arguably outperforms MOND and has a larger domain of applicability, but like MOND and unlike Deur's analysis, is a purely phenomenological theory without a solid theoretical basis behind it. The formulas derived by each of the investigators is not all that different, which is reassuring (and, of course, necessary for the formulas to match reality). There has been at least one serious effort, however, to reproduce MOG in a manner with a more solid theoretical basis that is generalized to address dark energy as well.
One powerful new dark matter data point we are likely to get in 2015 is increasingly precise data on Milky Way dynamics in previously unobservable parts of our galaxy that can be used to more precisely model a hypothetical Milky Way dark matter halo, and to fine tune modified gravity model parameters.
* A good place to start the discussion, however, is with a 2014 summary of the state of warm dark matter and cold dark matter models:
Recent high-resolution simulations that include Cold Dark Matter (CDM) and baryons have shown that baryonic physics can dramatically alter the dark matter structure of galaxies. These results modify our predictions for observed galaxy evolution and structure. Given these updated expectations, it is timely to re-examine observational constraints on the dark matter model. A few observations are reviewed that may indirectly trace dark matter, and may help confirm or deny possible dark matter models. Warm Dark Matter (WDM) and Self-Interacting Dark Matter (SIDM) are currently the favorite alternative models to CDM. Constraints on the WDM particle mass require it to be so heavy that WDM is nearly indistinguishable from CDM. The best observational test of SIDM is likely to be in the dark matter distribution of faint dwarf galaxies, but there is a lack of theoretical predictions for galaxy structure in SIDM that account for the role of baryons.Alyson Brooks, "Re-Examining Astrophysical Constraints on the Dark Matter Model" (July 28, 2014).
SIDM models, because they introduce a new force and not just a new particle, also fair less well in Occam's Razor relative to gravity modification models, than simple singlet dark matter models that struggle mightily to be reconciled with empirical data, for which the consensus is that the answer is "warm dark matter or bust."
A year later, Brooks is co-author of an article that compares CDM to SIDM in simulations with baryonic matter feedback and finds that the differences are surprisingly modest.
This past November, Brooks noted that baryonic feedback can help to partially explain the surprisingly number of bulgeless galaxies that are observed, but still struggles to reproduce the relative number of bulgeless and bulgeful galaxies which are observed in real life. Stating that:
After reviewing the results of relevant research that has been published to date, we use cosmological simulations to explore the ability of feedback to reduce or even prevent bulge growth during mergers. In dwarf galaxies, mergers actually reduce the central concentration of galaxies as the induced burst of star formation drives out low angular momentum material. This result shows the potential for feedback to reduce central mass growth. However, we also demonstrate that it is very difficult for current stellar feedback models to reproduce the small bulges observed in more massive disk galaxies like the Milky Way. We argue that feedback models need to be improved, or an additional source of feedback such as AGN is necessary to generate the required outflows.The large number of bulgeless galaxies is not nearly so challenging for modified gravity theories.
Friday, December 18, 2015
14 kya Archaic Hominin Remins Found In SW China
The number of Late Pleistocene hominin species and the timing of their extinction are issues receiving renewed attention following genomic evidence for interbreeding between the ancestors of some living humans and archaic taxa. Yet, major gaps in the fossil record and uncertainties surrounding the age of key fossils have meant that these questions remain poorly understood.
Here we describe and compare a highly unusual femur from Late Pleistocene sediments at Maludong (Yunnan), Southwest China, recovered along with cranial remains that exhibit a mixture of anatomically modern human and archaic traits. Our studies show that the Maludong femur has affinities to archaic hominins, especially Lower Pleistocene femora. However, the scarcity of later Middle and Late Pleistocene archaic remains in East Asia makes an assessment of systematically relevant character states difficult, warranting caution in assigning the specimen to a species at this time. The Maludong fossil probably samples an archaic population that survived until around 14,000 years ago in the biogeographically complex region of Southwest China.Darren Curnoe et al., "A Hominin Femur with Archaic Affinities from the Late Pleistocene of Southwest China", PLoS ONE 10(12): e0143332 (December 18, 2005) (open access) via Dienekes' Anthropology Blog.
The site where the femur was found is better known as "Red Deer Cave" (which is what the Chinese name translates to). Another blog notes that:
Analysis of a 14,000 year-old partial human femur found in 1989 from the Maludong (Red Deer) Cave in the Yunnan, Southwest China states that the femur looks like that of early Homo erectus and H. habilis… Way more archaic in morphology than the dating implies. . . .
In 2012 the team published their analysis of the skull bones from the site. They speculated the bones could represent an unknown new species, or perhaps a very early and primitive-looking population of modern humans, which had migrated to the region more than 100,000 years ago.
The thigh bone is more primitive than the skulls seem. The shaft is narrow and long with a thin cortex that is buttressed. This discovery is controversial because, until now, it had been thought that the youngest pre-modern humans on mainland Eurasia (Neanderthals and Denisovans) died out 40,000 years ago, soon after anatomically modern Homo sapiens entered the region. But… This find hints at the possibility a pre-modern species may have overlapped in time with modern humans on mainland East Asia.
Figure 2: Scatterplots comparing sample medians for subtrochanteric (ST) variables, neck-shaft angle and reconstructed body mass: (A) Anteroposterior (AP) diameter (mm). (B) Mediolateral (ML) diameter (mm). (C) Total area (TA: mm2). (D) Cortical area (CA: mm2). (E) %-Cortical area (%-CA). (F) Platymeric index (%). (G) Neck-shaft angle (°). (H) Reconstructed body mass (kg). (Error bars = 95% confidence interval of median [dark] and 1.5 x interquartile range [light]; Abbreviations: LPHO = Lower Pleistocene Homo; MPHO = Middle Pleistocene Homo; NEAN = Neanderthals; MPMH = Middle Pleistocene Modern Humans; EULU = Early Upper-Late Upper Palaeolithic.
Figure 4: Object plot from principal component analysis of 10 continuous variables: PC1 (52.85%) versus PC2 (28.92%) (AMH femora labeled in black; archaic hominins in blue; minimal spanning tree shown). [Ed. the new sample from 14,000 years ago is MLDG 1678 which shows clear affinity in the PCA chart to the archaic as opposed to the modern human femers.]
Figure 5. [Ed. The neighbor joining tree analysis likewise shows a strong affinity of the new sample to very archaic Homo Erectus femers.]
The opening of the paper notes (emphasis added) that:
The number of Late Pleistocene archaic hominin species, their biogeographical distribution, and the timing of their extinction remain important but intractable questions in palaeoanthropology. These issues have been brought into sharp relief over the last half-decade following the accumulation of genomic evidence for interbreeding between the Pleistocene ancestors of living humans and archaic hominins across much of the Old World. Yet, in many regions, archaic remains are sparse or absent from the Late Pleistocene fossil record.
The few exceptions include: 1) the Neanderthals (H. neanderthalensis) in Europe, West Asia, and extending at times into southern Siberia, the youngest example being from Mezmaiskaya dating ~39 ka; 2) possibly the North African specimens Dar-es-Soltane and Témara from Morocco, with a reported age range of ~110 to 40–20 ka for the associated Aterian lithic industry; 3) fossils from Denisova Cave in southern Siberia consisting of a molar and manual and pedal phalanges that have been dated >50 ka, and whose phylogenetic position has been inferred from recovered genomic DNA sequences to be the sister species to the Neanderthals; 4) fragmentary cranial, mandibular and dental remains from Xujiayao in North China dating in the range of ~125–60 ka, and exhibiting a unique morphology including some similarities to Neanderthals; and 5) in Southeast Asia, H. floresiensis at Liang Bua Cave, Flores, dating ~74–17 ka, with its similarities to Lower Pleistocene and Pliocene hominins.
The dearth of Late Pleistocene archaic fossils makes the identification of a number of the species involved in episodes of interbreeding with early anatomically modern humans (AMH) problematic. One prominent example is the occurrence of “Denisovan” DNA in the genomes of some contemporary humans in East Asia and Australo-Melanesia suggesting their Pleistocene ancestors interbred with this anatomically poorly known taxon. While no fossils beyond Denisova Cave have been identified as belonging to this group, Denisovan mitochondrial diversity combined with the observed strong geographic patterning of Denisovan DNA in living people imply they were formerly widespread with a range extending perhaps into Southeast Asia.
Additionally, genomic research has shown that Neanderthals contributed more DNA to contemporary East Asians than Europeans indicating that multiple episodes of interbreeding must have occurred under a model of complex admixture and demographic scenarios across a wide geographic area. Yet, there is presently no direct evidence for their occupation of Asia anywhere east of the Altai Mountains. While some East Asian Middle Pleistocene remains like those from Maba in South China might show affinities to Neanderthals, they are probably too old to be related to the “classic” Neanderthals. Yet, other interpretations of the morphology of Chinese Middle Pleistocene fossils such as from Dali have proposed a role for gene flow between archaic hominins and AMH in the emergence of recent East Asian populations.
Pinpointing the extinction date for archaic hominins is also important for understanding the adaptive and demographic responses of these species to the arrival of AMH beyond rare interbreeding events. As hominins fit the definition of megafauna, the circumstances surrounding their extinction also potentially adds to understanding of the impacts AMH had on the environment during the Late Pleistocene and their potential role in the demise of a wide range of large-bodied mammal species.
Several of the current authors have previously reported the occurrence of hominin cranial remains from two sites in Southwest China (Maludong and Longlin or Laomaocao Cave) that combine archaic hominin and AMH traits. In the case of the unusual cranium from Longlin Cave, it was recently concluded that its mosaic morphology probably results from hybridisation between AMH and an unknown archaic species, perhaps even occurring during the early Holocene. A similar explanation might also apply to the morphology of the Maludong cranial fossils, a hypothesis currently under investigation by us.The individual probably weighed about 110 pounds (50 kilograms).
Here we report a partial proximal femur from Maludong (Yunnan), Southwest China, found in association with these unusual cranial remains, which shows morphological and phylogenetic affinities to archaic hominins. The Maludong hominins were all recovered from sediments dated with AMS 14C of charcoal to between about 14,310±340 cal. yr BP and 13,590±160 cal. yr BP. Thus, the Maludong femur is the youngest fossil with archaic morphology found to date and potentially extends the overlap of AMH and archaic hominins in East Asia to >50 ka.
The paper closes with these remarks:
Putting the results of our analyses together, MLDG 1678 shows morphological and phylogenetic affinities to archaic femora, particularly Lower Pleistocene early Homo. We conclude, therefore, that the Maludong femur represents an individual that probably belonged to an archaic taxon rather than AMH. Just which taxon it represents is difficult to determine, however, because of the scarcity of Late Pleistocene hominin femora from East Asia. It also remains unclear whether Late Pleistocene archaic groups from western Eurasia provide the most appropriate model for East Asian hominins during this period. In the case of AMH, though, we did include femora from East Asia, including the four from Minatogawa, and MLDG 1678 was found to be very distinct from them.Analysis
It is intriguing that such a plesiomorphic hominin could have survived at Maludong until near the end of the Pleistocene. Yet, this finding applies also to H. floresiensis, with its apparent minimum geological age only slightly older than MLDG 1678. Homo floresiensis has only been found on the island of Flores in eastern Indonesia though, and its occurrence has been explained by island biogeography. Moreover, the Maludong femur is distinct from the highly unusual femora of this species, with its unique mosaic of traits including resemblances to Australopithecus taxa. One possible explanation is that the Maludong femur samples the population presently known only from Denisova Cave in the Altai region and dubbed the “Denisovans”. Another candidate is the presently unnamed taxon represented by the Xujiayao fossils. However, the absence of femora from both of these groups makes these scenarios impossible to test at present. Besides, the similarities of MLDG 1678 to Lower Pleistocene
hominins implies that other possibilities should be considered, such as a late surviving descendent of a Lower Pleistocene East Asian group or even the Dmanisi hominins.
Yunnan Province is characterised by complex topography associated with Himalayan uplift and extrusion of the Indochina block resulting in vicarious biogeographic divisions. It is one of 20 floristic endemic centres in China, comprising subtropical evergreen broad-leaved and sclerophyllous forests, and contains high levels of palaeoendemism. The region around Maludong is also biogeographically on the northern edge of tropical Southeast Asia. Thus, the Maludong femur might represent a relic, tropically adapted, archaic population that survived relatively late in the biogeographically complex region of Southwest China.
These remains appear to be archaic hominins, or at least hybrids of modern humans and hominins with high levels of archaic admixture which are dated to a time period 30,000 more years after we would have any reason to suspect their existence. Unless these individuals were Denisovans or modern human-Denisovan hybrids, there is no trace of archaic hominin admixture from such a species in modern humans in East Asia or elsewhere.
The simplest explanation would be that while Homo Erectus was almost wiped out almost everywhere ca. 100,000-50,000 year ago, that a relict population survived but admixed with modern humans shortly after their arrival (or upon a later first contact with modern humans) in South China, and that this relict population survived but did not expand meaningfully for tens of thousands of years after all other Homo Erectus went extinct, before this population too went extinct in the Mesolithic era or early Holocene era, perhaps because the adoption of farming and herding by modern humans during the Neolithic Revolution in China tipped the balance such that modern humans wiped out these hybrid Homo Erectus individuals.
Of course, yet another possibility is that the dating or the analysis assigning these features to archaic genetic admixture are flawed in some respect or another. Since the claim that this find seems to support is so extraordinary, the proof that must support it for it to be accepted as accurate must also be extraordinary.
Background: Modern Humans Outside Africa
It is undisputed that modern humans has entered crossed the Wallace line into places like Flores, Papua New Guinea, and Australia, probably from India via Southeast Asia, by 55,000 years ago, and there is one set of modern human remains in mainland Southeast Asia dated to around 65,000 years ago, but not very definitively. There is strong, although not completely incontrovertible evidence, that the same group of modern humans were present in India continuously both before and after the massive volcanic Toba eruption that took place ca. 75,000 years ago.
The earliest signs of modern humans outside of Africa, in the form of tools and other relics, are in Arabia, date to ca. 120,000 years ago and show affinities to a modern human archaeological culture in Nubia. The earliest remains that appear to be modern human outside of Africa are from Israel and date to about 100,000 years ago. But, conventional wisdom holds that this population represents either an Out of Africa migration that failed, or one that did not significantly expand, until much later.
There are several cases in which bones that appear to be modern human from Southern China have been dated to 100,000 years ago or more, despite the fact that conventional wisdom would not expect any modern human remains in Southern China until about 73,000 years ago (a couple of thousand years after the Toba eruption which seems to have cleared the way for modern humans to enter Southeast Asia and East Asia via a Southern route). There are a small number of remains and relics associated with Homo Erectus in Southeast Asia and East Asia up to about 100,000 years ago.
Conventional wisdom had been that the overlap was due to bad dating, and the older of the 100,000+ year old modern human finds in South China were tainted with poor archaeological methodology and the specter that there was pressure to bend the data to support the Chinese Communist government's favored "multi-regional evolution" theory (which is mostly not true, although archaic admixture has modestly complicated a pure Out of Africa theory of modern human evolution).
But, the lack of archaic Homo Erectus admixture in mainland Southeast and East Asia, and the lack of significant overlap between the period in which remains and relics associated with Homo Erectus and remains and relics associated with modern humans are found in Southeast Asia and East Asia, until now has strongly supported the inference that the complete extinction of Homo Erectus (apart of Homo Florensis if they are related) accompanied the appearance of modern humans in Southeast Asia and East Asia.
Of course, the low levels of non-Neanderthal archaic admixture in mainland Southeast Asia and East Asia could instead be due to a high level of dilution of first wave modern human populations by later waves of migrants to mainland Southeast Asia and East Asia after archaic hominins were extinct or moribund in the region. Indeed, this dilution almost certainly did take place, although the extent to which modern humans in Southeast Asia and East Asia are derived genetically from the first wave of migrations is hard to assess with any great accuracy.
Given the near total absence of data, it is also possible that Denisovans rather than modern humans, caused the extinction of Homo Erectus and may have even briefly replaced Homo Erectus before modern humans became predominant in Southeast Asia and East Asia, and simply did not leave any remains or relics that Asian archaeologists have found yet.
Background: A Brief Summary of Archaic Hominin Archaeology
Hominins evolved in Africa in a complex several million year story through many intermediate species, some of which coexisted in Africa at the same time, and others of which ended up going extinct without leaving descendant species.
Modern humans derive (in Africa ca. 250,000 years ago) from a species that evolved from Homo Erectus, a species evolves in Africa ca. 2,000,000 years ago that is also a remote ancestor of Neanderthals and probably all other non-African hominins.
The Lower Pleistocene era, begins around the time that Homo Erectus evolves. Homo Erectus expands into Africa around 1.8 million years ago (the type fossil for Homo Erectus is from the island of Java around 1.8 million years ago). The Lower Pleistocene era ends around the time that Neanderthals emerge, a few hundred thousand years ago. There is no convincing evidence of further significant evolution of Homo Erectus once it reaches Asia, although the evidence isn't rich enough to confirm or deny this hypothesis either.
The Middle Pleistocene era is basically the time period during which Neanderthals thrived in Eurasia from the Atlantic in the West, to Central Europe and Southern Siberia in the North, to India in the East, to Levant and Arabia in the South. As discussed more later, all modern humans outside Africa have low levels of Neanderthal admixture and a recent ancient DNA find from Ethiopia concluded that most Africans also have lower levels of Neanderthal admixture probably from relatively recent admixture with non-African modern humans.
In Southeast Asia and East Asia during the Middle Pleistocene era, Homo Erectus was the dominant hominin species, while Neanderthals reigned in Europe and modern humans were starting to emerge in Africa. Southeast Asia and East Asia area also has less advanced stone tools than are found in areas where Neanderthals were present.
A few hundred thousand years before the Neanderthals evolved, there is a European hominin species known as Homo Heidelbergus which evolved from Homo Erectus. It was once widely assumed that Homo Heidelbergus was ancestral to Neanderthals, but recent ancient DNA evidence has cast doubt on this conventional wisdom. The true story probably isn't that simple.
The youngest archaic hominin remains, other than Homo Florensis (a.k.a. Hobbit) remains on the island of Flores, anywhere east of India are about 100,000 years old. Neanderthals go extinct around 29,000 years ago in Southeast Europe or West Asia. Neanderthals and modern humans co-existed in Europe from about 42,000 years ago to 29,000 years ago, although not nearly so long in any one place. Neanderthals and modern humans co-existed earlier than that in SW Asia and West Asia (and perhaps India or part of India and Central Asia as well).
We have good whole genome data from a handful of bones of a hominin called Denisovans, after the cave where the ancient DNA was found, which were a sister clade of Neanderthals genetically. But, vexingly, we have too little data to reconstruct a skeleton of one or to even make much sense of their material culture and hunting habits.
Substantial Denisovan admixture is present thousands of miles away from Southern Siberia where this ancient DNA was found in aboriginal Australians and Papuans, lower levels are found in Negrito populations in the Philippines, and trace levels are found in East Asia, Tibet, the Americas, mainland Southeast Asia, and island Southeast Asia (although it is absent in India, the Andaman Islands and West Eurasia). Denisovans could be a highly derived species of late Eurasian Homo Erectus, a derived species of Neanderthals or their ancestor, or could be related to Homo Heidelbergus, or could be a hybrid of some of these, or could be some previously unattested hominin species that is none of the above.
The Denisovan DNA shows what are arguably traces of both Neanderthal and Homo Erectus admixture (with much more of the former than the latter). If this conclusion is correct, than Denisovans could not themselves have been Homo Erectus and the genetic evidence tends to point to a much more recent origin for this hominin species than the 2 million years that we would expect for Homo Erectus.
Homo Florensis is probably either a subspecies of Homo Erectus that experience island dwarfism, or a representative of the Denisovans (with or without island dwarfism), or a hybrid of the two, or both, or some entirely different kind of hominin species. No ancient Homo Florensis DNA has been successfully obtained.
We have statistical traces of recent low levels of admixture with unidentified archaic hominins in the population genetics of a couple of African populations.
Background: The Genetic Evidence
Genetic evidence (including recent ancient DNA evidence that can use non-mutation rate methods to determine the time of the most recent Neanderthal admixture of the ancestors of a Paleolithic modern human in Northern Europe) points to ages for the most basal Y-DNA and mtDNA haplogroups that are ancestral to all non-African modern humans, and to Neanderthal admixture which is shared by all non-African modern humans in roughly similar amounts to sometime on the order of 75,000 to 50,000 years ago, at the dawn of the Upper Paleolithic era, or the tail end of the Middle Paleolithic era (a.k.a. the Middle Pleistocene).
Y-DNA
Y-DNA haplogroups A, B and E are predominantly African in distribution and likely originate there.
All predominantly non-African Y-DNA haplogroups except Y-DNA haplogroups C and D are derived from Y-DNA haplogroup F, which most likely expands from a center of expansion in India. Y-DNA C likely also expanded from India to the East, although it is sometimes found at low frequencies in ancient European DNA. Y-DNA C and F have a deep common ancestor in Y-DNA CF.
Y-DNA D has an odd distribution. It is found in trace frequencies in West Africans (where the haplogroup that is the common ancestor of Y-DNA haplogroups D and E called Y-DNA DE* is also found), is predominant among indigenous Andamanese Islanders, is found at moderate frequencies among the people of Tibet (where Y-DNA DE* is also found), is found at low to moderate frequencies in various Paleo-North Asian populations, and is found at a high frequency of a highly diverged branch of Y-DNA D in Japan. Thus, Y-DNA D may indicate either a relict of an early Northern route migration by modern humans, or a maritime expansion that eventually worked its way inland to relatively unpopulated areas.
mtDNA
All non-African mtDNA haplogroups derive from the most basal forms of mtDNA M and N which is sister clades to various other clades of mtDNA L3 which is a predominantly African mtDNA haplogroup. mtDNA M has a predominantly Asian distribution quite similar to Y-DNA haplogroup C except for mtDNA M1 which has a predominantly North African and East African overlapping heavily with certain haplogroups of Y-DNA E and the Afro-Asiatic linguistic area that almost surely represented an Upper Paloelithic back migration of modern humans to Africa (and coincides with time depth with the probably separate back migration of mtDNA U6 to Africa).
Thursday, December 17, 2015
Interpretations of 750 GeV Bump Abound
Ten preprints were filed explaining the 750 GeV bump the day that it was announced (which is most often abbreviated as a particle described with the symbol S (for scalar)) and eight more preprints were filed the following day. UPDATE December 20, 2015: Twenty more papers were posted on the 18th. In addition, both Jester and Marco Frasca have advanced interpretations not clearly expressed in preprints in their respective blogs. The six Higgs bosons theory was also noted and dismissed without meaningful analysis by Lubos Motl at his blog.
Marco Frasca is the only voice out there arguing that there is any way that this bump could be consistent with the Standard Model Lagrangian by any means other than the six Higgs boson route, and thus has staked out what is for the most part the most conservative take on the news. Of course, there are lots of voices out there arguing that it isn't too late for the 750 GeV bump to turn out to be a fluke with the 145 GeV potential Higgs boson bump in the early days of the LHC which was offered up as a very comparable bump in terms of significance and character that didn't end up amounting to anything in the end.
In addition to the theories that I have described previously, the possibility that this is an axion, a graviton-like particle, or a Goldstone boson associated with supersymmetry breaking (or superpartner of one) have been raised. Composite particle analysis has been extended to consider a heavy pion or pion-like composite particle.
Still, to mangle an old saw, publication is the most sincere sign of credibility. We would not be deluged with the amount of fairly high quality instant analysis (often with multiple authors) that we have seen in the last couple of days if professionals in the HEP community weren't taking the 750 GeV bump very seriously.
I am inclined to think that the assumption that any tensor particle that can decay to a diphoton must be a graviton of some type, made by many of commentators is wrong (e.g. consider the counterexample to prove the point even if it isn't particularly likely, of a highly excited tensor glueball). Also though it is worth noting that any particle with neutral electric charge that can decay in a diphoton mode must do so through a triangle diagram, because neutral particles themselves don't couple to photons.
There is a definite "who ordered that" air to the entire discussion. While multiple papers have proposed some relationship between this bump and dark matter, it is far too heavy to be a credible dark matter candidate or and is far too heavy to even be a credible dark matter self-interaction force carrying boson. And, there really isn't any phenomenology gap other than the appearance of the bump itself, that we need to explain with this particle or something very much like it. This particle does not naturally recommend itself to solving any of the important unsolved questions in physics that we were looking for solutions to when it was observed.
Also, I should mention that the announcement also places strict limits on SUSY theories with many of the preprint authors acknowledging that the 750 GeV bump, if true, completely rules out the entire parameter space of the Minimal Supersymmetric Standard Model (MSSM). String theorists and SUSY supporters have retreated to the NMSSM (next to minimal supersymmetric standard model) barricades for the time being.
VAGUELY RELATED:
* Meson width (which is the inverse of half-life in the proper units) is related to temperature under some leading numerical approximations of QCD by as much as a factor of fifty. This result could be relevant to the many questions that have arisen over whether the 750 GeV bump is consistent with a Higgs like boson based upon its width, as the unprecedented energy scales of the latest data may have an impact on effective temperature which in turn can influence width and has probably not been widely adjusted for by early commentators.
* The never ending battle to measure the QCD coupling constant continues, although its current accuracy isn't that impressive. The current world average is down a bit to 0.1177 +/- 0.13 (about 1%) which is down by about 0.0007 from the previous world average. The real interesting question, however, is not the actual mean value of the QCD coupling constant (even though that is more interesting than it seems), but whether the running of the QCD coupling constant with energy scale is consistent with the Standard Model prediction, or differs as it does in almost all grand unification theories including SUSY.
META NOTE: With this post, both Dispatches at Turtle Island and its sister blog Wash Park Prophet have more posts in 2015 than they did in either 2014 or 2013.
UPDATE December 19, 2015: A 750 GeV Higgs boson could secure that vacuum stability that is merely metastable with a single 126 GeV Higgs boson.
Marco Frasca is the only voice out there arguing that there is any way that this bump could be consistent with the Standard Model Lagrangian by any means other than the six Higgs boson route, and thus has staked out what is for the most part the most conservative take on the news. Of course, there are lots of voices out there arguing that it isn't too late for the 750 GeV bump to turn out to be a fluke with the 145 GeV potential Higgs boson bump in the early days of the LHC which was offered up as a very comparable bump in terms of significance and character that didn't end up amounting to anything in the end.
In addition to the theories that I have described previously, the possibility that this is an axion, a graviton-like particle, or a Goldstone boson associated with supersymmetry breaking (or superpartner of one) have been raised. Composite particle analysis has been extended to consider a heavy pion or pion-like composite particle.
Still, to mangle an old saw, publication is the most sincere sign of credibility. We would not be deluged with the amount of fairly high quality instant analysis (often with multiple authors) that we have seen in the last couple of days if professionals in the HEP community weren't taking the 750 GeV bump very seriously.
I am inclined to think that the assumption that any tensor particle that can decay to a diphoton must be a graviton of some type, made by many of commentators is wrong (e.g. consider the counterexample to prove the point even if it isn't particularly likely, of a highly excited tensor glueball). Also though it is worth noting that any particle with neutral electric charge that can decay in a diphoton mode must do so through a triangle diagram, because neutral particles themselves don't couple to photons.
There is a definite "who ordered that" air to the entire discussion. While multiple papers have proposed some relationship between this bump and dark matter, it is far too heavy to be a credible dark matter candidate or and is far too heavy to even be a credible dark matter self-interaction force carrying boson. And, there really isn't any phenomenology gap other than the appearance of the bump itself, that we need to explain with this particle or something very much like it. This particle does not naturally recommend itself to solving any of the important unsolved questions in physics that we were looking for solutions to when it was observed.
Also, I should mention that the announcement also places strict limits on SUSY theories with many of the preprint authors acknowledging that the 750 GeV bump, if true, completely rules out the entire parameter space of the Minimal Supersymmetric Standard Model (MSSM). String theorists and SUSY supporters have retreated to the NMSSM (next to minimal supersymmetric standard model) barricades for the time being.
VAGUELY RELATED:
* Meson width (which is the inverse of half-life in the proper units) is related to temperature under some leading numerical approximations of QCD by as much as a factor of fifty. This result could be relevant to the many questions that have arisen over whether the 750 GeV bump is consistent with a Higgs like boson based upon its width, as the unprecedented energy scales of the latest data may have an impact on effective temperature which in turn can influence width and has probably not been widely adjusted for by early commentators.
* The never ending battle to measure the QCD coupling constant continues, although its current accuracy isn't that impressive. The current world average is down a bit to 0.1177 +/- 0.13 (about 1%) which is down by about 0.0007 from the previous world average. The real interesting question, however, is not the actual mean value of the QCD coupling constant (even though that is more interesting than it seems), but whether the running of the QCD coupling constant with energy scale is consistent with the Standard Model prediction, or differs as it does in almost all grand unification theories including SUSY.
META NOTE: With this post, both Dispatches at Turtle Island and its sister blog Wash Park Prophet have more posts in 2015 than they did in either 2014 or 2013.
UPDATE December 19, 2015: A 750 GeV Higgs boson could secure that vacuum stability that is merely metastable with a single 126 GeV Higgs boson.
Tuesday, December 15, 2015
Dagestani Genetics
Dagestan, in the Caucasus Mountains, has many linguistic groups and ethnicities. A recent study examined the population genetics of the modern inhabitants of Dagestan. Genetic differences more closely track linguistic differences than geography.
Y-DNA distinctions were particularly great with Y-DNA haplogroups J1-M267*, R1b-L23, G2a-U1, and R1a-Z93 appearing particularly prominent in some subpopulations. The first two of most distinctive of the Nakh language speaking people, with the contributions of the other two being relatively minor and the percentages of J1-M267* being greater than that of R1b-L23. In PCA analysis, Dagestani Y-DNA shows a cline from Europe to Central and South Asia to the Near East to Dagistan.
The mtDNA mix was more uniform across the region crossing linguistic boundaries, suggesting a history of bride exchange with geographically nearby groups. In PCA analysis, Europe's mtDNA looks like a subset of much more diverse Dagestani mtDNA, there is modest overlap with Near Eastern mtDNA, and the mtDNA of Central and South Asia overlaps modestly with the Near East, but not at all with that of Dagestan which encompasses all of the mtDNA diversity of Europe and more.
There were also significant autosomal genetic distinctions between the subpopulations and a Tree-Mix analysis showed little evidence of meaningful admixture between the subpopulations. In a PCA analysis, Dagestani autosomal genetics are surrounded by a ring of geographically nearby populations - clockwise, Central and South Asians, Near Easterners, Europeans, and other Caucasian (a group in turn adjacent to Central and South Asians).
Mutation based efforts to identify the age of the populations based upon their genetic diversity suggest that the Nakh language speaking people of Dagestan are descendants of the original Neolithic farmers of the region and date to about 6000-6650 years ago, an estimate consistent with the estimate based upon linguistic analysis of differences between languages in that language family.
Y-DNA distinctions were particularly great with Y-DNA haplogroups J1-M267*, R1b-L23, G2a-U1, and R1a-Z93 appearing particularly prominent in some subpopulations. The first two of most distinctive of the Nakh language speaking people, with the contributions of the other two being relatively minor and the percentages of J1-M267* being greater than that of R1b-L23. In PCA analysis, Dagestani Y-DNA shows a cline from Europe to Central and South Asia to the Near East to Dagistan.
The mtDNA mix was more uniform across the region crossing linguistic boundaries, suggesting a history of bride exchange with geographically nearby groups. In PCA analysis, Europe's mtDNA looks like a subset of much more diverse Dagestani mtDNA, there is modest overlap with Near Eastern mtDNA, and the mtDNA of Central and South Asia overlaps modestly with the Near East, but not at all with that of Dagestan which encompasses all of the mtDNA diversity of Europe and more.
There were also significant autosomal genetic distinctions between the subpopulations and a Tree-Mix analysis showed little evidence of meaningful admixture between the subpopulations. In a PCA analysis, Dagestani autosomal genetics are surrounded by a ring of geographically nearby populations - clockwise, Central and South Asians, Near Easterners, Europeans, and other Caucasian (a group in turn adjacent to Central and South Asians).
Mutation based efforts to identify the age of the populations based upon their genetic diversity suggest that the Nakh language speaking people of Dagestan are descendants of the original Neolithic farmers of the region and date to about 6000-6650 years ago, an estimate consistent with the estimate based upon linguistic analysis of differences between languages in that language family.
Credible Evidence Of A Beyond The Standard Model 750 GeV Mass Boson
The Resonance Signal and Its Significance
The ATLAS experiment at the large hadron collider (LHC) has seen a signal at 3.5 sigma significance of a potential new particle with a mass of about 750 GeV/c^2 in diphoton events. The CMS experiment has also seen a signal, of about 2 sigma significance, in diphoton events of roughly the same mass. The diphoton channel is a particularly clean way to discovery new particles because there is not much background from Standard Model events to interfere at that mass scale. CMS has also seen a 2.5 sigma signal at roughly the same mass in the charged lepton-neutrino-quark-anti-quark pair channel.
The data from the individual experiments standing alone and after considering look elsewhere effects, is not that significant, but the confirmation from two independent experiments makes these moderately significant bumps seem much more significant. While this doesn't amount to the discovery of a new particle (considered to be 5 sigma evidence), it is the most credible evidence yet that there could be a new particle.
I would put the likelihood of this resonance being real at about 45%, and the likelihood of this resonance being both real and unexplainable by Standard Model physics (e.g. for it not being a Standard Model composite particle of some sort) at about 35%.
Apparent Properties
As a consequence of conservation of intrinsic angular momentum (colloquially called "spin" even though that term has multiple other meanings), a particle that decays in the diphoton channel would have to be either "scalar" or "pseudo-scalar" (i.e. spin-0), or tensor (i.e. spin-2), and would have to have zero electric charge.
In other words, this particle looks a lot like a heavy Higgs boson. It is also hard to reconcile a heavy Higgs boson which would be expected to have a wide width, with the narrow apparent width of the "bumps" that are actually seen (the width is about 40 GeV). There is also no particularly well motivated reason to think that this would be a graviton resonance, even though that could, in principle, produce a spin-2, zero charge diphoton resonance.
Potential Theoretical Explanations
Most prosaically, this could be a case where six ordinary Standard Model Higgs bosons are produced at the same time (e.g. through the fusion of multiple gluons at once) and they are synchronized or superimposed upon each other in some manner that causes their combined decay product to be a diphoton decay. It could be that there are similar bumps at 250 GeV and 500 GeV but that those have not been as apparent because of much larger backgrounds at lower energies.
Supersymmetry (aka SUSY) and a lot of other beyond the Standard Model theories predict the existence of "two Higgs doublets", with a total of five Higgs bosons, a positively charged one, a negatively charged one, an extra "scalar" Higgs boson, and an extra "pseudoscalar" Higgs boson.
Marco Frasca, a physicist whose primary interest is QCD, meanwhile, has argued that the Standard Model Higgs boson should have an infinite number of higher energy excitations.
While lots of models predict such a particle, however, there is less clarity over what kind of couplings this particle would have to other particles (i.e. "what does this particle do?"), and many predict that an extra Higgs boson would be accompanied by other particles (often lighter than the heavy Higgs boson) that have not been discovered.
Importance, If Real
In a lot of ways, a new fundamental particle at 750 GeV would be far more significant than the discovery of the Standard Model Higgs boson.
The Standard Model Higgs boson was predicted to exist forty years before it was discovered and was necessary to the consistency and good functioning of the rest of the Standard Model. When it was discovered, every fundamental particle in the Standard Model had been discovered and none of the particles not predicted by the Standard Model had been discovered.
If there is a new fundamental particle at 750 GeV, however, this is definitive evidence of beyond the Standard Model physics of some kind, although the extensions could be very narrow, for example, in the model that Marco Frasca suggests, or very broad, for example, in the case of non-minimal supersymmetry.
Of course, it is also possible that this signal could be some non-fundamental particle (e.g. an excited state of a spin-0 glueball or an excited state of top quark quarkonia) which would still be very interesting, but far less interesting than a new fundamental particle.
As usual, the next step is watchful waiting as the ATLAS and CMS experimenters do their jobs.
Coverage Elsewhere
Jester has more analysis. Physics Forum discusses it here. Not Even Wrong coverage here. Matt Strassler is cautious and skeptical. Dorigo discusses the results but has little analysis.
Footnote
Today is the last day that the LHC was collect data in 2015. It will start operations again and start collecting more data sometime around April in the year 2016.
The ATLAS experiment at the large hadron collider (LHC) has seen a signal at 3.5 sigma significance of a potential new particle with a mass of about 750 GeV/c^2 in diphoton events. The CMS experiment has also seen a signal, of about 2 sigma significance, in diphoton events of roughly the same mass. The diphoton channel is a particularly clean way to discovery new particles because there is not much background from Standard Model events to interfere at that mass scale. CMS has also seen a 2.5 sigma signal at roughly the same mass in the charged lepton-neutrino-quark-anti-quark pair channel.
The data from the individual experiments standing alone and after considering look elsewhere effects, is not that significant, but the confirmation from two independent experiments makes these moderately significant bumps seem much more significant. While this doesn't amount to the discovery of a new particle (considered to be 5 sigma evidence), it is the most credible evidence yet that there could be a new particle.
I would put the likelihood of this resonance being real at about 45%, and the likelihood of this resonance being both real and unexplainable by Standard Model physics (e.g. for it not being a Standard Model composite particle of some sort) at about 35%.
Apparent Properties
As a consequence of conservation of intrinsic angular momentum (colloquially called "spin" even though that term has multiple other meanings), a particle that decays in the diphoton channel would have to be either "scalar" or "pseudo-scalar" (i.e. spin-0), or tensor (i.e. spin-2), and would have to have zero electric charge.
In other words, this particle looks a lot like a heavy Higgs boson. It is also hard to reconcile a heavy Higgs boson which would be expected to have a wide width, with the narrow apparent width of the "bumps" that are actually seen (the width is about 40 GeV). There is also no particularly well motivated reason to think that this would be a graviton resonance, even though that could, in principle, produce a spin-2, zero charge diphoton resonance.
Potential Theoretical Explanations
Most prosaically, this could be a case where six ordinary Standard Model Higgs bosons are produced at the same time (e.g. through the fusion of multiple gluons at once) and they are synchronized or superimposed upon each other in some manner that causes their combined decay product to be a diphoton decay. It could be that there are similar bumps at 250 GeV and 500 GeV but that those have not been as apparent because of much larger backgrounds at lower energies.
Supersymmetry (aka SUSY) and a lot of other beyond the Standard Model theories predict the existence of "two Higgs doublets", with a total of five Higgs bosons, a positively charged one, a negatively charged one, an extra "scalar" Higgs boson, and an extra "pseudoscalar" Higgs boson.
Marco Frasca, a physicist whose primary interest is QCD, meanwhile, has argued that the Standard Model Higgs boson should have an infinite number of higher energy excitations.
While lots of models predict such a particle, however, there is less clarity over what kind of couplings this particle would have to other particles (i.e. "what does this particle do?"), and many predict that an extra Higgs boson would be accompanied by other particles (often lighter than the heavy Higgs boson) that have not been discovered.
Importance, If Real
In a lot of ways, a new fundamental particle at 750 GeV would be far more significant than the discovery of the Standard Model Higgs boson.
The Standard Model Higgs boson was predicted to exist forty years before it was discovered and was necessary to the consistency and good functioning of the rest of the Standard Model. When it was discovered, every fundamental particle in the Standard Model had been discovered and none of the particles not predicted by the Standard Model had been discovered.
If there is a new fundamental particle at 750 GeV, however, this is definitive evidence of beyond the Standard Model physics of some kind, although the extensions could be very narrow, for example, in the model that Marco Frasca suggests, or very broad, for example, in the case of non-minimal supersymmetry.
Of course, it is also possible that this signal could be some non-fundamental particle (e.g. an excited state of a spin-0 glueball or an excited state of top quark quarkonia) which would still be very interesting, but far less interesting than a new fundamental particle.
As usual, the next step is watchful waiting as the ATLAS and CMS experimenters do their jobs.
Coverage Elsewhere
Jester has more analysis. Physics Forum discusses it here. Not Even Wrong coverage here. Matt Strassler is cautious and skeptical. Dorigo discusses the results but has little analysis.
Footnote
Today is the last day that the LHC was collect data in 2015. It will start operations again and start collecting more data sometime around April in the year 2016.
Monday, December 14, 2015
Fitness Enhancing Archaic Genes May Have Much Wider Distribution
For the most part, genetic traces of admixture between Denisovans and modern humans are found in people with Papuan or Australian Aboriginal descent.
But, select fitness enhancing genes, such as one related to the distribution of body fat on a person, match a gene found in Denisovans, have a much wider distribution. This gene is found in Native Americans and mainland Asians which have little or no trace Denisovan ancestry otherwise and is particularly adaptive to arctic and high altitude conditions.
While other sources of these gene are possible (e.g. independent evolution of the same gene more than once), a source in archaic hominins seems likely. If a gene has strong fitness enhancing effects, it isn't uncommon for it to reach fixation or at least significant proportions in a population, even if genes that are selectively neutral are almost sure to disappear through genetic drift in the same circumstances.
But, select fitness enhancing genes, such as one related to the distribution of body fat on a person, match a gene found in Denisovans, have a much wider distribution. This gene is found in Native Americans and mainland Asians which have little or no trace Denisovan ancestry otherwise and is particularly adaptive to arctic and high altitude conditions.
While other sources of these gene are possible (e.g. independent evolution of the same gene more than once), a source in archaic hominins seems likely. If a gene has strong fitness enhancing effects, it isn't uncommon for it to reach fixation or at least significant proportions in a population, even if genes that are selectively neutral are almost sure to disappear through genetic drift in the same circumstances.
Sunday, December 13, 2015
Evidence For Violent Indo-European Replacement
Ancient DNA has decisively established that there was at least one major demographic shift in Europe between the arrival of the first farmers in the Early Neolithic era and modern Europe. Further ancient DNA data has pretty much pinned this down to the Middle or Late Neolithic era to early Bronze Age time frame. At least in Central and Eastern Europe, this transition very likely involved incoming Indo-Europeans.
There has been great debate over the extent to which this was a peaceful transition (e.g. with the first farmers dying off and leaving a vacuum this is filled peacefully by a second wave of metal using people), or a case of violent conquest. The data is inconclusive, but one recent data point argues for the violent conquest/genocide theory.
A grave containing multiple victims of what appears to have been a violent raid where even women ad children had extremities hacked off in the time frame where this transition took place, suggests that this transition may have been a violent one.
There has been great debate over the extent to which this was a peaceful transition (e.g. with the first farmers dying off and leaving a vacuum this is filled peacefully by a second wave of metal using people), or a case of violent conquest. The data is inconclusive, but one recent data point argues for the violent conquest/genocide theory.
A grave containing multiple victims of what appears to have been a violent raid where even women ad children had extremities hacked off in the time frame where this transition took place, suggests that this transition may have been a violent one.
SUSY-GUT Upper Bound For Energy Scale Proposed
An analysis of the latest data from the LHC proposes that there is an upper bound on the mass of the lightest supersymmetric particle of about 20 TeV (ten to a hundred times current exclusion levels of the minimum mass of such particles).
We state that, if the SUSY-GUT paradigm holds, the mass of lightest gluino or higgsino cannot be larger than about 20 TeV. Such a limit is strongly dependent on the measurement of the strong coupling at the electroweak energy scale and on the proton decay limit.While this bound is impossible to reach at the LHC, it suggests and attainable energy scale at which SUSY theories could be disproved.
Wednesday, December 9, 2015
Indo-European Ethnogenesis?
What would cause a society to give rise to a new language and culture that would become proto-Indo-European and when and where did this happen?
One of the strongest candidates for this ethnogenesis, which merged first farmer Neolithic peoples descended from Anatolians with Caucasian and Eastern hunter-gatherer populations, is that it happened as a result of widespread intermarriage across these cultural barriers in the Tripolye-Sredniy Stog archaeological cultures.
Evidence for this hypothesis is offered in a materials quoted in a recent post at the Eurogenes blog.
One of the strongest candidates for this ethnogenesis, which merged first farmer Neolithic peoples descended from Anatolians with Caucasian and Eastern hunter-gatherer populations, is that it happened as a result of widespread intermarriage across these cultural barriers in the Tripolye-Sredniy Stog archaeological cultures.
Evidence for this hypothesis is offered in a materials quoted in a recent post at the Eurogenes blog.
Refined LHC Top Quark Mass Measurements Now Available
The best available estimate of the mass of the top quark from the Large Hadron Collider (LHC) combining data from both the CMS and ATLAS experiments is now 172.38 +/- 0.66 GeV. The final Tevatron mass measurement for the top quark was 174.34 +/- 0.64 GeV. This brings the error weighted world average mass measurement of the top quark to about 173.35 GeV, which is consistent with both the LHC measurement and the Tevatron measurement at the 1.5 sigma level.
The previous top quark mass estimate from ATLAS (as of April of 2015) was 172.99 +/- 0.91 GeV. The latest combined LHC measurement excluding that ATLAS estimate was 173.34 +/- 0.76 GeV. Thus, the LHC mass measurement is trending down.
As noted in the Tevatron mass estimate post:
The previous top quark mass estimate from ATLAS (as of April of 2015) was 172.99 +/- 0.91 GeV. The latest combined LHC measurement excluding that ATLAS estimate was 173.34 +/- 0.76 GeV. Thus, the LHC mass measurement is trending down.
As noted in the Tevatron mass estimate post:
The expected value of the top mass from the formula that the sum of the square of each of the fundamental particle masses equals the square of the Higgs vaccum expectation value, given the state of the art Higgs boson mass measurement (and using a global fit value of 80.376 GeV for the W boson rather than the PDG value) is 173.73 GeV. . . . If the the sum of the square of the boson masses equals the sum of the square of the fermion masses the implied top quark mass is 174.03 GeV if pole masses of the quarks are used, and 174.05 GeV if MS masses at typical scales are used.Thus, there are theoretical conjectures that pull the expected value of the top quark mass up from the current estimates, although those estimates are not in great tension with the current global average.
Tuesday, December 8, 2015
The Population Genetics Of Modern France
A new comprehensive study of the autosomal population genetics of modern France is notable, because for various reasons France is underrepresented compared to other parts of Europe in population genetic studies.
But, the study doesn't tell us much except that generally population genetics within France vary in a clinal manner that is quite predictable, and that Paris is a bit of an exception to that since it draws people who are ancestrally from all over France and beyond.
The study does nothing to place France in a larger European or regional context, or to compare modern French population genetics to ancient DNA samples in Europe or otherwise. It isn't clear to me if the data has been made publicly available so that others may engage in the analysis that the authors of this study refrained from doing themselves.
In the absence of this analysis, it is also hard to say what this detailed genetic data says about the population history of the French people. The study also contains no analysis, linked to the autosomal data or otherwise, of uni-parental markers or particular alleles associated with particular phenotypes (such as skin and eye color or lactose tolerance).
So, on the whole the existence of the data is very tempting, but what has been done with it so far is very disappointing.
But, the study doesn't tell us much except that generally population genetics within France vary in a clinal manner that is quite predictable, and that Paris is a bit of an exception to that since it draws people who are ancestrally from all over France and beyond.
The study does nothing to place France in a larger European or regional context, or to compare modern French population genetics to ancient DNA samples in Europe or otherwise. It isn't clear to me if the data has been made publicly available so that others may engage in the analysis that the authors of this study refrained from doing themselves.
In the absence of this analysis, it is also hard to say what this detailed genetic data says about the population history of the French people. The study also contains no analysis, linked to the autosomal data or otherwise, of uni-parental markers or particular alleles associated with particular phenotypes (such as skin and eye color or lactose tolerance).
So, on the whole the existence of the data is very tempting, but what has been done with it so far is very disappointing.
Friday, December 4, 2015
The Mechanisms of Linguistic Diversity
A blog post does a solid job of setting forth the conventional wisdom regarding why linguistic diversity emerges and survives which I recently set forth in a much less comprehensive and unsourced well in some recent blog comments myself.
In a nutshell, languages grow more elaborate over time due to random habitual noise that gets trimmed back when there are significant numbers of adult foreign language learners whose imperfect language learning ability tends to result in the simplification of the language (and in substrate influences).
For the most part, to borrow evolutionary language, the differences in the choices languages make about their grammars are selective fitness neutral with no intrinsic benefits or detriments, and have no particular relationship to other cultural practices of a community except by virtue of historical accident due to the communities having common origins.
Furthermore, communities also intentionally differentiate themselves from other communities linguistically to allow for identification and communication of in group members while excluding and concealing communications from outsiders.
In a nutshell, languages grow more elaborate over time due to random habitual noise that gets trimmed back when there are significant numbers of adult foreign language learners whose imperfect language learning ability tends to result in the simplification of the language (and in substrate influences).
For the most part, to borrow evolutionary language, the differences in the choices languages make about their grammars are selective fitness neutral with no intrinsic benefits or detriments, and have no particular relationship to other cultural practices of a community except by virtue of historical accident due to the communities having common origins.
Furthermore, communities also intentionally differentiate themselves from other communities linguistically to allow for identification and communication of in group members while excluding and concealing communications from outsiders.
Still No New Physics At LHC
Lubos explains (with humor that is in somewhat bad taste as he allegorically compares the new physics theories that have been ruled out to terrorist mass shooting victims), that LHC Run 2 data from the CMS experiment have increased the range of masses for which various kinds of beyond the Standard Model hypothetical particles are ruled out by about 40% (on average) over the exclusions in place at the end of Run 1.
The Standard Model continues to explain all phenomena observed to within the error bars of the accuracy of the measurement after adequately accounting for look elsewhere effects.
The exclusions for the kinds of hypothetical particles searched for are for all such particles up to 2.6 TeV to 7 TeV, depending upon the type of particle in question, which is favor above the "Fermi scale" at which the heaviest electroweak fundamental particles are observed, but far below the GUT scale or Planck scale at which a unification of forces or fundamental limitations on energy scales might be encountered (which no human designed experiment has any realistic chance of ever reaching).
The exclusions will in all likelihood continue to grow larger as further data is collected at the LHC.
The Standard Model continues to explain all phenomena observed to within the error bars of the accuracy of the measurement after adequately accounting for look elsewhere effects.
The exclusions for the kinds of hypothetical particles searched for are for all such particles up to 2.6 TeV to 7 TeV, depending upon the type of particle in question, which is favor above the "Fermi scale" at which the heaviest electroweak fundamental particles are observed, but far below the GUT scale or Planck scale at which a unification of forces or fundamental limitations on energy scales might be encountered (which no human designed experiment has any realistic chance of ever reaching).
The exclusions will in all likelihood continue to grow larger as further data is collected at the LHC.
Tuesday, December 1, 2015
Chasing Fundamental Physics
Several recent preprints take a stab at considering deeper order that could give rise to the constants of the Standard Model.
One considers a non-supersymmetric alternative to a key assumption of quantum chromodynamics (QCD) in the Standard Model that governs the strong force. Francesco Sannio's unusually well written article, "Challenging Asymptotic Freedom" (submitted November 29, 2015) considers a change to how the strong force coupling constant runs at high energies, which is consistent with experimental data from particle physics experiments, but would make the low energy QCD behavior known as "asymptotic freedom" merely an approximate effective description of how the strong force acts, rather than an assumption that is rigorously true at all energy scales, with deep implications for cosmology and very high energy physics. The abstract of that article reads as follows:
But, these articles do prove, by example, that there are viable and fruitful paths for theoretical physicists to explore that do not involve supersymmetry and that could provide a path forward to a deeper understanding of the deeper fundamental physics that give rise to the Standard Model after half a century of work with supersymmetry theories and string theory seem to have done nothing but lead us into a theoretical rabbit hole.
Last week, Jester at the Resonaances blog explored the extent to which experimental evidence is consistent with Leptoquarks, another non-SUSY beyond the Standard Model theory which isn't a bad fit to several current moderately statistically significant anomalies at the LHC, but which few people, myself included, are very excited about as a theory. Lubos explores the angle with decidedly more enthusiasm, although even he, in the end, admits he doesn't really think that this will prove to be the correct interpretation of the data.
Finally, I will note an interesting more rigorous treatment of what Hawking Radiation really is at the Backreaction blog the explains in which respects the heuristic explanation given by Stephen Hawking in his book, "A Brief History of Time" actually oversimplifies the reality as it has been understood by physicists since the 1970s and how it is related to the Unruh effect which is another truly weird consequence of the intersection of relativity and quantum physics.
One considers a non-supersymmetric alternative to a key assumption of quantum chromodynamics (QCD) in the Standard Model that governs the strong force. Francesco Sannio's unusually well written article, "Challenging Asymptotic Freedom" (submitted November 29, 2015) considers a change to how the strong force coupling constant runs at high energies, which is consistent with experimental data from particle physics experiments, but would make the low energy QCD behavior known as "asymptotic freedom" merely an approximate effective description of how the strong force acts, rather than an assumption that is rigorously true at all energy scales, with deep implications for cosmology and very high energy physics. The abstract of that article reads as follows:
Several extensions of the standard model feature new colored states that besides modifying the running of the QCD coupling could even lead to the loss of asymptotic freedom. Such a loss would potentially diminish the Wilsonian fundamental value of the theory. However, the recent discovery of complete asymptotically safe vector-like theories, i.e. featuring an interacting UV fixed point in all couplings, elevates these theories to a fundamental status and opens the door to alternative UV completions of (parts of) the standard model. If, for example, QCD rather than being asymptotically free becomes asymptotically safe there would be consequences on the early time evolution of the Universe (the QCD plasma would not be free). It is therefore important to test, both directly and indirectly, the strong coupling running at the highest possible energies. I will review here the attempts made in to use pure QCD observables at the Large Hadron Collider (LHC) to place bounds on new colored states. Such bounds do not depend on the detailed properties of the new hypothetical states but on their effective number and mass. We will see that these direct constraints cannot exclude a potentially safe, rather than free, QCD asymptotic nature. A safe QCD scenario would imply that quarks and gluons are only approximately free at some intermediate energies, otherwise they are always in chains.An article by Yithsbey Giraldo, "Five-Zero Texture non-Fritzsch like Quark Mass Matrices in the Standard Model" (submitted November 28, 2015) explores a rather unambitious theoretical approach that, if true, would remove one of the ten experimentally measured parameters (the six quark masses and four CKM matrix parameters) that are found in the Standard Model. Its abstract says:
We will consider a five-zero texture non-Fritzsch like quark mass matrices that is completely valid and generates all the physical quantities involved, including the quark masses, the Jarlskog invariant quantity and the inner angles of the Cabibbo-Kobayashi-Maskawa unitarity triangle, and explaining the charge parity violation phenomenon at 1σ confidence level. To achieve this, non-physical phases must be included in the unitary matrices used to diagonalize the quark mass matrices, in order to put the Cabibbo-Kobayashi-Maskawa matrix in standard form. Besides, these phases can be rotated away so they do not have any physical meaning. Thus, the model has a total of nine parameters to reproduce ten physical quantities, which implies physical relationships between the quark masses and/or mixings.Finally, an article by Venkitesh Ayyar and Shailesh Chandrasekharan, "Origin of fermion masses without spontaneous symmetry breaking"(submitted on November 29, 2015) explores an unconventional mechanism that could impart mass to fundamental fermions in the Standard Model. It's abstract is as follows:
Using a simple three dimensional lattice four-fermion model we argue that massless fermions can become massive due to interactions without the need for any spontaneous symmetry breaking. Using large scale Monte Carlo calculations within our model, we show that this non-traditional mass generation mechanism occurs at a second order quantum critical point that separates phases with the same symmetries. Universality then suggests that the new origin for the fermion mass should be of wide interest.All three preprints are basically speculative theoretical proposals with almost no impact on any of the experimental data points in particle physics to date. The odds of any particular one of them being right are modest.
But, these articles do prove, by example, that there are viable and fruitful paths for theoretical physicists to explore that do not involve supersymmetry and that could provide a path forward to a deeper understanding of the deeper fundamental physics that give rise to the Standard Model after half a century of work with supersymmetry theories and string theory seem to have done nothing but lead us into a theoretical rabbit hole.
Last week, Jester at the Resonaances blog explored the extent to which experimental evidence is consistent with Leptoquarks, another non-SUSY beyond the Standard Model theory which isn't a bad fit to several current moderately statistically significant anomalies at the LHC, but which few people, myself included, are very excited about as a theory. Lubos explores the angle with decidedly more enthusiasm, although even he, in the end, admits he doesn't really think that this will prove to be the correct interpretation of the data.
Finally, I will note an interesting more rigorous treatment of what Hawking Radiation really is at the Backreaction blog the explains in which respects the heuristic explanation given by Stephen Hawking in his book, "A Brief History of Time" actually oversimplifies the reality as it has been understood by physicists since the 1970s and how it is related to the Unruh effect which is another truly weird consequence of the intersection of relativity and quantum physics.
Quick Hits
* The mtDNA atlas blog has only five posts so far, but the content and comments on those posts are thoughtful and well worth reading.
* Geocurrents has a fascinating post on regional variation in religious beliefs in Japan with comparisons to the South Korean situation. These regional variations appear to reflect the deep historical roots of modern Japan and include animist practices in one area that may reflect pre-Yayoi religious beliefs.
The situation in Japan is complicated by the fact that religious traditions normally considered to be entirely different faiths are followed by the same individuals in different domains of life. Syncretism is pervasive. Hence, a typical Japanese person may, for example, simultaneously have a Buddhist funeral and pray at Shinto shrines from time to time during life, while following a basically secular Confucian set of social norms. Query how much this reflects a more general strategy with which Japanese culture has historically chosen a path of selective assimilation in language, culture, and genetic admixture with indigenous populations as well.
This may seem anomalous, but it is less so when one considers analogous instances of Americans who simultaneously consider themselves to be Christian while observing folk traditions with deep "pagan" roots. For example, most American Christians celebrate both the resurrection of Christ and "pagan" Easter Bunny traditions at Easter, and celebrate both the birth of Christ and Santa Clause traditions at Christmas.
South Korea, generally speaking, is less syncretic. A person's identity as a Christian, a Buddhist, or a secular person is more distinct at the individual level.
Historically, both Christian identification was not present in meaningful numbers until the 20th century during which it became the most Christian country in Asia due to Christianity's role as an institution facilitating positive political change.
Before that, Korean history tells the story of epic battles that have seen one side and then the other ascendant, between metaphysically secular Confucianists and the intrusive institutions of Buddhist missionaries which have been welcomed during some Korean regimes and persecuted in other regimes, that goes back many, many centuries.
The article does not mention the role of "pagan" practices akin to animistic Chinese folk religion in Korea,[1] perhaps because few people today now self-identify in that way religiously. But, I know from my own extended family lore that these practices were common place and were taken very seriously at least as late as the 1960s at least among Korea's senior citizens, even by people who self-identified religiously as Christian or Buddhist, and that some practices which are on the line between "superstition", "tradition" and "religion", for example, consulting soothsayers and astrologers when naming children, persist in Korea even today, even among people who self-identify as Christian. So the extent to which Korea is syncretic may have more to do with state of mind than it does with actual practice.
[1] I am making some assumptions in the analogy to Chinese folk religion based upon geography and the source of the once prevailing Confucian belief system in Korea. But, an alternative hypothesis is that the "pagan" Korean practices of which I am aware have a cryptic source in Japanese Shinto and folk religious belief, rather than Chinese folk religion, and that they became a part of my own extended family's belief system and traditions during the period of Japanese occupation of Japan, but are not actually widely shared among Koreans outside my extended family. The existence of cryptic Japanese genetic ancestry in this part of my extended family would be consistent with this alternative hypothesis. But, I lack sufficient information about this part of the family lore, and I also lack sufficient information about syncretic religious practice plays out in daily life for other ordinary Koreans, to evaluate the relatively likelihood of these alternatives very accurately. Finally, of course, it is entirely possible that Japanese Shinto practice is itself a direct elaboration of Chinese folk religion at some point in early Japanese history that did not persist in the same way in China, in which case the distinction that I am making in this footnote between the two may be something of a category error.
* Scholarly conjectures on the language abilities of Neanderthals are considered. John Hawks also has a nice piece on the bigger picture of ancient admixture among our ancient ancestors and are more recent ancestors belong to our own species. He is a bit more more vague that I would like, however, in his discussion of "ghost populations." He references one of his 2006 journal articles in support of some of the concepts in his post.
* Humans who lived in Florida ten thousand years ago responded to changing sea levels.
* Anthropologists have securely dated traces of human occupation in Australia to at least 53,000 years ago at a new site in a cave on Barrow Island which is now off the Australian coast but would have been part of the continent at the time.
* There are large stone wheels in the Middle East from Syria to Saudi Arabia first sited by airplane pilots in 1927 that appear to be observatories or calendars of some sort and are made with varying degrees of precision. The oldest have now been dated to 8,500 years ago (6,500 BCE) and continuing in use until at least 5,500 years ago (3,500 BCE) if not later, at a time when the local climate was more favorable. Realistically, in that area and given the climate at the time, these dates suggest that they were built by farmers in the early Neolithic era, rather than by hunters and gatherers in the pre-farming Mesolithic era (even though other finds demonstrate that Middle Eastern hunter-gatherers did have permanent outdoor temple-like structures before domesticated plants were farmed anywhere on Earth).
* First there was a growing awareness of gut bacteria communities. Now, we know that even expresso machine waste bins develop stable bacterial communities (that are quite distinct from machine to machine) over time. More generally, this points to another place where scientists can look for genetic evidence about the human past. While it seems far fetched to be able to recover ancient gut bacteria, scientists have already recovered ancient disease bacteria from well preserved mass plague burial sites.
* Geocurrents has a fascinating post on regional variation in religious beliefs in Japan with comparisons to the South Korean situation. These regional variations appear to reflect the deep historical roots of modern Japan and include animist practices in one area that may reflect pre-Yayoi religious beliefs.
The situation in Japan is complicated by the fact that religious traditions normally considered to be entirely different faiths are followed by the same individuals in different domains of life. Syncretism is pervasive. Hence, a typical Japanese person may, for example, simultaneously have a Buddhist funeral and pray at Shinto shrines from time to time during life, while following a basically secular Confucian set of social norms. Query how much this reflects a more general strategy with which Japanese culture has historically chosen a path of selective assimilation in language, culture, and genetic admixture with indigenous populations as well.
This may seem anomalous, but it is less so when one considers analogous instances of Americans who simultaneously consider themselves to be Christian while observing folk traditions with deep "pagan" roots. For example, most American Christians celebrate both the resurrection of Christ and "pagan" Easter Bunny traditions at Easter, and celebrate both the birth of Christ and Santa Clause traditions at Christmas.
South Korea, generally speaking, is less syncretic. A person's identity as a Christian, a Buddhist, or a secular person is more distinct at the individual level.
Historically, both Christian identification was not present in meaningful numbers until the 20th century during which it became the most Christian country in Asia due to Christianity's role as an institution facilitating positive political change.
Before that, Korean history tells the story of epic battles that have seen one side and then the other ascendant, between metaphysically secular Confucianists and the intrusive institutions of Buddhist missionaries which have been welcomed during some Korean regimes and persecuted in other regimes, that goes back many, many centuries.
The article does not mention the role of "pagan" practices akin to animistic Chinese folk religion in Korea,[1] perhaps because few people today now self-identify in that way religiously. But, I know from my own extended family lore that these practices were common place and were taken very seriously at least as late as the 1960s at least among Korea's senior citizens, even by people who self-identified religiously as Christian or Buddhist, and that some practices which are on the line between "superstition", "tradition" and "religion", for example, consulting soothsayers and astrologers when naming children, persist in Korea even today, even among people who self-identify as Christian. So the extent to which Korea is syncretic may have more to do with state of mind than it does with actual practice.
[1] I am making some assumptions in the analogy to Chinese folk religion based upon geography and the source of the once prevailing Confucian belief system in Korea. But, an alternative hypothesis is that the "pagan" Korean practices of which I am aware have a cryptic source in Japanese Shinto and folk religious belief, rather than Chinese folk religion, and that they became a part of my own extended family's belief system and traditions during the period of Japanese occupation of Japan, but are not actually widely shared among Koreans outside my extended family. The existence of cryptic Japanese genetic ancestry in this part of my extended family would be consistent with this alternative hypothesis. But, I lack sufficient information about this part of the family lore, and I also lack sufficient information about syncretic religious practice plays out in daily life for other ordinary Koreans, to evaluate the relatively likelihood of these alternatives very accurately. Finally, of course, it is entirely possible that Japanese Shinto practice is itself a direct elaboration of Chinese folk religion at some point in early Japanese history that did not persist in the same way in China, in which case the distinction that I am making in this footnote between the two may be something of a category error.
* Scholarly conjectures on the language abilities of Neanderthals are considered. John Hawks also has a nice piece on the bigger picture of ancient admixture among our ancient ancestors and are more recent ancestors belong to our own species. He is a bit more more vague that I would like, however, in his discussion of "ghost populations." He references one of his 2006 journal articles in support of some of the concepts in his post.
* Humans who lived in Florida ten thousand years ago responded to changing sea levels.
* Anthropologists have securely dated traces of human occupation in Australia to at least 53,000 years ago at a new site in a cave on Barrow Island which is now off the Australian coast but would have been part of the continent at the time.
* There are large stone wheels in the Middle East from Syria to Saudi Arabia first sited by airplane pilots in 1927 that appear to be observatories or calendars of some sort and are made with varying degrees of precision. The oldest have now been dated to 8,500 years ago (6,500 BCE) and continuing in use until at least 5,500 years ago (3,500 BCE) if not later, at a time when the local climate was more favorable. Realistically, in that area and given the climate at the time, these dates suggest that they were built by farmers in the early Neolithic era, rather than by hunters and gatherers in the pre-farming Mesolithic era (even though other finds demonstrate that Middle Eastern hunter-gatherers did have permanent outdoor temple-like structures before domesticated plants were farmed anywhere on Earth).
* First there was a growing awareness of gut bacteria communities. Now, we know that even expresso machine waste bins develop stable bacterial communities (that are quite distinct from machine to machine) over time. More generally, this points to another place where scientists can look for genetic evidence about the human past. While it seems far fetched to be able to recover ancient gut bacteria, scientists have already recovered ancient disease bacteria from well preserved mass plague burial sites.
Civilization As A Consequence Of War
Peter Turchin's new book, Ultrasociety, argues that modern large scale civilization is something that has emerged largely as a tool developed because it was necessary for warfare. The book also provides fun facts like the fact that socially complex ants makes up a combined 25% of the mass of all animals on Earth, which is a pretty interesting fact and an interesting way to measure the dominance of different kinds of organisms.
This builds on model based research described in in 2013 PNAS paper which is open access that I read and discussed, either at this blog or in comments elsewhere at the time. The abstract of the paper reads as follows:
If I recall correctly, the guts of the model as applied also exploit a recurring motif in forest level views of history - conflict between "barbarian" herder societies (often in mountains or dry steppes) that tend to prevail in "bad times" and "civilized" farmer societies that tend to prevail when conditions are more optimal.
The other question, of course, is whether we as a species have outgrown this kind of dynamic, or if it continues to drive our cultural evolution on more or less the same basis that it did from the late Bronze Age through the Middle Ages.
This builds on model based research described in in 2013 PNAS paper which is open access that I read and discussed, either at this blog or in comments elsewhere at the time. The abstract of the paper reads as follows:
How did human societies evolve from small groups, integrated by face-to-face cooperation, to huge anonymous societies of today, typically organized as states? Why is there so much variation in the ability of different human populations to construct viable states?
Existing theories are usually formulated as verbal models and, as a result, do not yield sharply defined, quantitative predictions that could be unambiguously tested with data.
Here we develop a cultural evolutionary model that predicts where and when the largest-scale complex societies arose in human history. The central premise of the model, which we test, is that costly institutions that enabled large human groups to function without splitting up evolved as a result of intense competition between societies—primarily warfare. Warfare intensity, in turn, depended on the spread of historically attested military technologies (e.g., chariots and cavalry) and on geographic factors (e.g., rugged landscape).
The model was simulated within a realistic landscape of the Afroeurasian landmass and its predictions were tested against a large dataset documenting the spatiotemporal distribution of historical large-scale societies in Afroeurasia between 1,500 BCE and 1,500 CE. The model-predicted pattern of spread of large-scale societies was very similar to the observed one. Overall, the model explained 65% of variance in the data. An alternative model, omitting the effect of diffusing military technologies, explained only 16% of variance.
Our results support theories that emphasize the role of institutions in state-building and suggest a possible explanation why a long history of statehood is positively correlated with political stability, institutional quality, and income per capita.I'm generally pretty skeptical of model based research of this kind, but Turchin's stochastic model is one of the best examples of the type, doing an excellent job of striking a balance between having too many and too few parameters, and of modeling them in a way that reproduces alternative histories that are similar in broad outlines to historical reality. The fact that the model can do so strongly suggests that the parameters that the model considers are basically the right ones.
If I recall correctly, the guts of the model as applied also exploit a recurring motif in forest level views of history - conflict between "barbarian" herder societies (often in mountains or dry steppes) that tend to prevail in "bad times" and "civilized" farmer societies that tend to prevail when conditions are more optimal.
The other question, of course, is whether we as a species have outgrown this kind of dynamic, or if it continues to drive our cultural evolution on more or less the same basis that it did from the late Bronze Age through the Middle Ages.