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.

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 individual probably weighed about 110 pounds (50 kilograms).

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.

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.

Analysis

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).

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.

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.

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.

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.

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.

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.

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.

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 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.

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.

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.

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.

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:

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.

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:

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.

Special Relativity and General Relativity Explained With A Ten Hundred Word Vocabulary

A quite lucid explanation of special relativity and general relativity with a limited vocabulary by Randall Munroe of xkcd fame has been reprinted at the New Yorker. A taste:

There once was a doctor with cool white hair. He was well known because he came up with some important ideas. He didn’t grow the cool hair until after he was done figuring that stuff out, but by the time everyone realized how good his ideas were, he had grown the hair, so that’s how everyone pictures him. He was so good at coming up with ideas that we use his name to mean “someone who’s good at thinking.”

Two of his biggest ideas were about how space and time work. This thing you’re reading right now explains those ideas using only the ten hundred words people use the most often. The doctor figured out the first idea while he was working in an office, and he figured out the second one ten years later, while he was working at a school. That second idea was a hundred years ago this year. (He also had a few other ideas that were just as important. People have spent a lot of time trying to figure out how he was so good at thinking.)

The first idea is called the special idea, because it covers only a few special parts of space and time. The other one—the big idea—covers all the stuff that is left out by the special idea. The big idea is a lot harder to understand than the special one. People who are good at numbers can use the special idea to answer questions pretty easily, but you have to know a lot about numbers to do anything with the big idea. To understand the big idea—the hard one—it helps to understand the special idea first.

Ancient DNA from Neolithic Greece and Anatolia

Investigators have managed to get right to the source of the European Neolithic Revolution with ancient DNA from Greece and Anatolia, which is described in two new papers.

Like all other Early European Farmers, genetically, they are quite similar to modern day Sardinians and lack the European and Central Asian steppe contribution that is ubiquitous in most modern European populations.

The Y-DNA in the Neolithic Greeks and Anatolians was, unsurprisingly G2a2.  The mtDNA of two Mesolithic individuals was K1c and the mtDNA of two Neolithic individuals was K1a2.

Of course, their genes look quite unlike modern Greeks and Turks.

Ancient And Modern Ideograms

The Language Log blog highlights the research of Genevieve Von Petzinger into the use of symbols that may be ideograms as a form of written proto-language in Upper Paleolithic cave art as described in a linked TED talk that she has given.

In a somewhat related point, somewhere on my blogging "to do" list is the task of figuring out how many ideograms are in common used by readers of American English, ideally accompanied by examples of the use of ideograms to convey a sound associated with the word for which the ideogram stands (in the tradition of military use of words like Victor or Charlie to spell out words in situations where radio transmission quality is poor) in languages that are predominantly ideographic.

The point, of course, would be to illustrate that the line between phonetic writing systems and ideographic writing systems is one of degree, rather than being an all out either/or alternative.

Some of the common ideograms in American English include:

@ "at"
#  "pound
$ "dollar"
% "percent"
& "and"
~ "approximately"
> "greater than"
< "less than"
= "equals"
+ "plus"
- "minus"

There are many other ideograms familiar to readers of American English that can't be produced with a single keystroke.

There are thousands of Chinese ideograms in the proto-typical ideogram based writing system (Coptic hieroglyphics being another such language).  But, I'd guess that the number of ideograms widely understood by readers of American English.

Some fields, such as mathematics, make particularly heavy use of ideograms which are typically global in reach across the lines of the languages of the people who use them.

Cosmology Based Limits On The Sum Of The Three Neutrino Masses Tighten

The Data

The sum of the three neutrino masses is less than or equal to 110 meV at a 95% confidence level, according to the latest effort to integrate multiple sources of astronomy data including the Planck satellite cosmic microwave radiation background data, the WiggleZ Dark Energy Survey, the Sloan Digital Sky Survey -Data Release 7 (SDSS-DR7) sample of Luminous Red Galaxies (LRG), and Baryon Acoustic Oscillation (BAO) data.

This is confirmed by an independent analysis of the Lyman-α power spectrum from BOSS cited in the paper, which limits the sum of the three neutrino masses to less than or equal to 120 meV at the 95% confidence level.

Background

In an inverted hierarchy of neutrino masses, the minimum sum of the three neutrino masses given current neutrino oscillation data is around 98 +/- 1 meV.

As previously noted at this blog, the state of the art measurements of the difference between the first and second neutrino mass eigenstate is roughly 8.66 +/- 0.12 meV, and the difference between the second and third neutrino mass eigenstate is roughly 49.5 +/- 0.5 meV, which implies that the sum of the three neutrino mass eigenstates cannot be less than about 65.34 meV with 95% confidence.

The hypothesis that there are more than three neutrinos that oscillate with each other has also been largely ruled out by experimental data.

Hypothesis Testing

Taken together, this data favors the normal neutrino mass hierarchy over the inverted neutrino mass hierarchy, even though the inverted neutrino mass hierarchy is not yet ruled out at a 95% confidence interval.

The body text of the paper does not expressly compare the relative likelihoods of the minimal mass normal hierarchy hypothesis to the minimal mass inverted hierarchy hypothesis, but, eyeballing the graphs with the pertinent data, it appears that the normal hierarchy is many times more likely than the inverted hierarchy.

Future Experiments

We need only about a 10% improvement in measurement precision to rule out the inverted neutrino mass hierarchy at the 95% confidence level.  We shouldn't be surprised that the neutrinos appear to have a normal mass hierarchy, as this is what we observe in the up-type quarks, the down-type quarks, and the charged leptons as well.

Knowing whether the neutrino mass eigenstates have a normal or inverted hierarchy also increases the certainty with which we can interpret neutrino oscillation data, for example, in an effort to determine the CP violating phase (if any) of neutrino oscillations.

The tight bound on the absolute neutrino masses discussed below also sets firm expectations regarding the expected amount of neutrinoless double beta decay in any particular model that has Majorana mass neutrinos.  Current experimental precision needs to improve by more than a factor of ten before it can meaningfully distinguish between Dirac and Majorana mass scenarios.

Bounds On Absolute Neutrino Masses Given What We Know

If the neutrinos do have a normal hierarchy, then the experimental bounds on the three neutrino mass eigenstates at the two sigma level based upon the latest data is:

v1: 0 meV to 12 meV              absolute precision +/- 6 meV
v2: 8.42 meV to 21.9 meV      absolute precision +/- 6.74 meV
v3: 56.92 meV to 72.4 meV    absolute precision +/- 7.74 meV

Any higher masses would violate the 110 meV upper bound on the sum of the three neutrino mass eigenstates.  So, while absolute neutrino mass has been called an "unsolved problem" we are tantalizingly close to determining it with a precision that is stunning in absolute terms and compares favorably with the precision with which we know the light quark masses in relative terms.

The bound between the minimum and maximum neutrino mass ranges in an inverted mass hierarchy is currently about 4.7 meV (i.e. +/- 2.35 meV for the lightest of the three).  If the neutrinos do indeed have an inverted mass hierarchy, the bounds upon the absolute masses are tight indeed.

An Unambitious Neutrino Mass Prediction

Given all of the data and the patterns that we see, I personally would be surprised to see anything other than a normal neutrino mass hierarchy with a lightest neutrino mass eigenstate of 2 eV or less, with a mass of 1 meV or less most favored. If that hypothesis is correct, then the neutrino masses would be:

v1: 0 meV to 2 meV          
v2: 8.42 meV to 11.9 meV    
v3: 56.92 meV to 62.4 meV

and the sum of the three neutrino masses would be not more than 76.3 meV (and not less than 65.34 meV).

Footnote On Inflation Constraints

In other news, the constraints on evidence of certain kinds of gravitational waves in the early universe which are predicted by inflation theories is also tightening considerably.  Generally speaking, this data tends to rule out many of the more elaborate inflation scenarios.

Hollywood Habits Reach Particle Physics

Usually, the abstract of a scientific journal article simply summarizes what the article says in a single paragraph (some longer, some shorter).  The main distinction among abstracts is between those that actually put their key conclusion in the lede, and those that bury the lede and tell you what the conclusion is about while forcing you to actually read the paper to get that result.

But, taking a cue from Hollywood, a researcher from the ALICE collaboration has gone one step further.  After the usual abstract telling you what the current paper says, she throws in one more sentence about coming attractions which are not actually included in the paper, stating: "Recent results obtained from these measurements will be presented and the measured cross sections will be compared to perturbative Quantum Chromodynamics calculations at next-to-leading order."

Now, admittedly, maybe she just means that they will present the results in this paper.  But, in context, it reads more to me like an announcement of an upcoming conference paper rather than a description of what is currently being presented.

New Denisovan DNA

Until now, we had one individual's Denisovan autosomal DNA and Denisovan mtDNA from two individuals.  Renanalysis of one of the teeth used the first time around and ancient DNA from a third morphologically similar tooth has given us new data.

We now have (partial) autosomal DNA from two more Denisovan individuals (the one who was the source of the mtDNA sample and a new individual) and a new set of Densiovan mtDNA (with a different haplogroup than the other two samples) from the same new individual.

This new DNA data confirm that all three teeth comes from individuals of the same Denisovan species of archaic hominin.

Denisovans appear to be a sister clade of archaic hominins to Neanderthals and all three samples come from a single cave in Siberia.  But, significant Denisovan admixture (in addition to the ordinary amount of Neanderthal mixture for East Eurasians) is present in modern humans with Australian Aboriginal ancestry or Papuan ancestry.  There may also be an independent source of Denisovan admixture in some Asian Negrito populations (e.g. in the Philippines, but not in the Andamanese) and possibly some very slight traces of Denisovan ancestry in modern humans in Southeast Asia and East Asia.  The introduction to the paper notes that:

In 2008, a finger phalanx from a child (Denisova 3) was found in Denisova Cave in the Altai Mountains in southern Siberia. The mitochondrial genome shared a common ancestor with presentday human and Neandertal mtDNAs about 1 million years ago, or about twice as long ago as the shared ancestor of present-day human and Neandertal mtDNAs. However, the nuclear genome revealed that this individual belonged to a sister group of Neandertals. This group was named Denisovans after the site where the bone was discovered. Analysis of the Denisovan genome showed that Denisovans have contributed on the order of 5% of the DNA to the genomes of present-day people in Oceania, and about 0.2% to the genomes of Native Americans and mainland Asians. 

In 2010, continued archaeological work in Denisova Cave resulted in the discovery of a toe phalanx (Denisova 5), identified on the basis of its genome sequence as Neandertal. The genome sequence allowed detailed analyses of the relationship of Denisovans and Neandertals to each other and to present-day humans. Although divergence times in terms of calendar years are unsure because of uncertainty about the human mutation rate, the bone showed that Denisovan and Neandertal populations split from each other on the order of four times further back in time than the deepest divergence among present-day human populations occurred; the ancestors of the two archaic groups split from the ancestors of present-day humans on the order of six times as long ago as present-day populations. In addition, a minimum of 0.5% of the genome of the Denisova 3 individual was derived from a Neandertal population more closely related to the Neandertal from Denisova Cave than to Neandertals from more western locations .

The abstract also notes that:

The mtDNA of Denisova 8 is more diverged and has accumulated fewer substitutions than the mtDNAs of the other two specimens, suggesting Denisovans were present in the region over an extended period. The nuclear DNA sequence diversity among the three Denisovans is comparable to that among six Neandertals, but lower than that among present-day humans. 

All of this is pretty much what we would expect from additional Denisovan DNA samples and none of them answer the big unsolved questions we have regarding the Denisovans, but it is still nice to have the additional data.

The one point I would add is that the more basal nature of the mtDNA from Denisovan 8 is used to argue that this tooth is much older and represents a prolonged occupations of the site.  This is not a necessary interpretation, or even, in my humble opinion, a likely one.

It is common for particular individuals in modern human populations living at the same time, to have both more basal and less basal mtDNA.  For example, in the same village in Nigeria, there might be one individual with mtDNA which most recently mutated 1,000 years ago, and another individual with mtDNA that most recently mutated 40,000 years ago.

This is an elementary inference from the apparent common mitochondrial origin of all hominins, and the fact that mutations happen with a low random frequency at each generation.  In any substantial sized population, the mtDNA sequence with the least recent mutation is likely to have last mutated many thousands of years earlier than the mtDNA sequence with the most recent mutation.

Given the archaeological context of the teeth, in similar layers of debris in a single cave, the likelihood that there was mtDNA diversity with both older and younger clades of mtDNA present seems more likely to me than a continuous occupation for thirty thousand or so years that managed to be deposited in such close proximity to each other.  One could estimate a predicted population size on this basis and compare it to the estimate using other methods.

The open access PNAS paper is here.  John Hawks has an analysis at his blog.

Connecting the Cultural Dots With Relics And Legends

Gruda Boljevića tumulus is one of the most important archaeological sites found recently in Europe. The reason why I believe that this tumulus is so important, is because it shows that the dolmen building, golden cross disc making culture which developed in Montenegro in the first half of the third millennium BC, has its direct cultural roots in Yamna culture of the Black Sea steppe. Why is this important?

I have already shown that the golden cross discs which appear in Ireland and Britain around 2500 BC have their predecessors in golden cross discs from Montenegro which were dated to 2700 BC (Mala Gruda) and some time between 3050 BC and 2700 BC (Gruda Boljevića). Considering that these golden cross discs first appear in Montenegro and then in Ireland and Britain and nowhere else in between suggests that this cultural trait could have been a result of a direct cultural transfer between Montenegro and Ireland and Britain. Irish archaeologists are reluctant to say whether this cultural influence was due to trade or missionary contacts, or whether it was a consequence of a migration of a group people into Ireland.

This is because Irish archaeologists don't read pseudo histories like the Irish annals. If they did they would have seen the old Irish annals tell us that right at the time when the metallurgy and the first golden cross discs appear in Ireland, a group of people, a tribe a clan lead by Partholón arrives in Ireland. Partholón and his people are credited with introducing cattle husbandry, plowing, cooking, dwellings, trade, and dividing the island in four and most importantly for this story, they are credited with bringing gold which before them was not used in Ireland. They bring the golden cross discs. But where did Partholón and his people come from? The Irish annals tell us that too. They tell us that Partholón arrived to Ireland from the Balkans via Iberia. The Lebor Gabála Érenn, an 11th-century Christian pseudo-history of Ireland, tells us more. It tells us that Partholón came to the Balkans from the Black Sea steppe, the land where at the beginning of the 3rd millennium BC we find Yamna culture...

From the Old European culture blog.

It has long been known that Iberians and remarkably similar genetically to the people of the British Isles, and that both populations are rich in Y-DNA R1b. It has also been recently discovered that the Yamna people had Y-DNA R1b, although more fine distinctions of sub-haplotypes of R1b muddy the connection between the Yamna people and Western Europeans.

It is much less well known, as observed in the comments to this post at the Eurogenes blog, the Croatians and the English, at least at a naive three ancestral component analysis level, seem to have very similar autosomal genetic makeups to each other.

Are the Irish legendary histories telling us the true tale of how the people bearing Y-DNA R1b came to arrive in Western Europe?

The Old European Culture blog, slowly and in individually intriguing and convincing installments is cumulatively making a convincing argument in that direction that can be corroborated with well dated archaeological relics. And, while this analysis doesn't name the Western European cultures involved, it does point to some very specific times and places to look for the culture that probably brought Y-DNA R1b to Europe along with a prominent role for cattle. This time and place turn out to be a pretty good fit to the Bell Beaker culture, while it is a rather poor fit to the megalithic culture that was already present when the Bell Beaker culture emerged.

The path suggested by Irish legendary history is notable, in part, because it is a match for one of several outstanding hypotheses for how Y-DNA R1b wound up in Western Europe, and also because legendary history from Ireland may be more reliable than in many other places because its position at an island isolated ocean frontier would have prevented it from being easily muddled with infusions of legendary histories from elsewhere.

This analysis also doesn't attach a definitively linguistic label to this population. Many scholars assume that the Yamna people of the steppe were Indo-Europeans, and there are some good reasons for that assumption. But, it is hardly definitive. While we have written Sumerian and Egyptian documents from this far back in history, we have no comparably old documents in any other languages.

The record is equally consistent with a hypothesis in which the Yamna people spoke a language that was in contact with Proto-Indo-European and borrowed words from it, but was itself non-Indo-European and related to one or more Caucasian languages. In this scenario, a non-Indo-European Yamna derived language arrives in Western Europe in the time frame, while Western Europe undergoes widespread language shift to Celtic or proto-Celtic languages much later, plus or minus a few centuries from Bronze Age collapse in most places. This scenario is attractive, because otherwise, the heavily Y-DNA R1b Basque people would have had to experience a language shift from an Indo-European language to Basque, which seems far less likely to be the case.

Some Musings About Nomeclature, Mesons And Forces

Almost all of the ordinary matter in the universe (as opposed to "dark matter") is made up of protons and neutrons assembled together into atomic nuclei of atoms with one or more protons and sometimes with sometimes also with some neutrons each.

The atom is completed with one electron per proton in orbit around the nucleus (strictly speaking, "orbit" is a bit misleading as a classical approximation of the actual quantum physics behavior of electrons associated with an atomic nucleus, but it is good enough for the purposes of this post).  If the correspondence between protons and electrons in an "atom" is other than one to one, it is conventional to use the term "ion" rather than "atom" to describe it.

Protons and neutrons are composite particles made up of three quarks each, which are bound together by gluons which are emitted and absorbed by the quarks in the proton or neutron respectively (the generic name that encompasses both protons and neutrons is a "nucleon" often abbreviated "N").

It turns out that protons and neutrons are actually just the two most common examples of a larger class of composite particles made up of three quarks bound together by gluons which are call "baryons".

There is a still more general class of composite particles made up of quarks (not necessarily three) that are bound together by gluons which are called "hadrons" (there is also a hypothetical class of composite particles made up solely of gluons bound together in the absence of quarks often called "glueballs", but I'm not sure if they count as hadrons or not).

Hadrons made up of two quarks (or of blended combinations of two quark pairs) are called "mesons", a term that was coined in the 1930s when the need for a force carrying particle to bind protons in atomic nuclei was hypothesized many years before the first meson was actually observed.

Mesons made up of two different kinds of quarks are usually named based upon the heaviest quark in the mesons.  When that quark is a bottom quark (formerly also known as a beauty quark), the meson is, logically, known as a B meson.  But, most of the lighter mesons were discovered and named before the quark theory of the Standard Model was worked out and the quarks were assigned names.  So, their names are quite arbitrary.

If the heaviest quark in a meson is a charm quark it is usually known as a D meson (but prior to 1986, a meson with a charm quark and a strange quark was known as an F meson). It is also curious that the physics community managed to abolish the historical irregular name for the D_s meson, but not many other of the historical irregular names of other hadrons.

If the heaviest quark in a meson is a strange quark, it is usually known as a "kaon" abbreviated "K".

If we were renaming mesons today, knowing what we do about the Standard Model, they would probably have been called S mesons, C mesons, and B mesons, respectively. But, historical accident and the immense amount of education needed to do the physics that makes knowing these names relevant has allowed the irregular historical monikers to survive.

Different naming conventions apply to "quarkonia", in which a meson and antimeson of the same flavor are both present.

I'd welcome comments from anyone who can explain how it is that Kaons, D mesons, F mesons and any of the other irregular hardon names were assigned (baryon naming, for what it is worth, has fewer irregular hadron names, perhaps because more of them were discovered after the quark model was in place).

As in other areas of language, irregular names for hadrons seem to have persisted more strongly for the most common mesons, than for the rare ones.

We still have arbitrary meson names not precisely tied to quark content for scalar and axial vector mesons, whose quark content is not well understood.

There are several kinds of mesons that contain only up and down quarks (or are at least dominantly comprised of up and down quarks).  The lightest are the pi mesons, also known as pions.  Another kind of meson containing only (or at least dominantly) up and down quarks is the rho meson.

Pions and rhos bring us from the land of history and language in physics to the land of QCD (the physics of the strong force that binds quarks with gluons called "quantum chromodynamics").

It turns out that the force hypothesized back in the 1930s that binds protons and neutrons into atomic nuclei called the "nuclear strong force" is not a fundamental force of nature.  Instead, it is basically a second order effect of the fundamental strong force which is mediated by gluons to hold hadrons together "leaking" out of hadrons to bind them to other nearby hadrons.

The nuclear strong force is mediated not by gluons, which are fundamental in the Standard Model, but by mesons, which are composite particles, although, like gluons, mesons are bosons (a class of particles that has one kind of quantum mechanical behavior) rather than fermions (a class of particles including all baryons and quarks and leptons such as electrons that has another kind of quantum mechanical behavior).

What caught my eye as I was looking into the history of the odd nomenclature of mesons was that while the nuclear strong force is mediated primarily (virtual) pions, it is also mediated in part by other kinds of mesons, especially (virtual) rhos.

This made me think about different kinds of mediator particles for different forces. Electromagnetism is mediated by photons, which are mostly identical, but can differ from each other in frequency, polariziation or helicity.  The strong force is mediated by gluons, which are also mostly identical to each other, but can come in eight different combinations of color charges.

The weak force, in contrast, is mediated by both W bosons (which come in W+ and W- varieties that are antiparticles of each other), and Z bosons which differ in mass and charge from W bosons.  In this respect, the weak force is a bit like the nuclear strong force, which has more than one kind of mediating boson, although the non-fundamental and emergent nuclear strong force, in principle at least within the Standard Model, can have more kinds of potential mediator mesons than the weak force had mediator weak force bosons.

It is interesting to consider how the Standard Model might be subtly modified to reflect the existence of additional weak force bosons that appear much less frequently the W and Z bosons in much the way that rhos and other mesons mediate the nuclear strong force much less frequently than pions do.

There are hypothetical W' and Z' particles which have been searched for experimentally (and thus far, not discovered).  But, it isn't entirely clear that those models are sufficient to account for the kinds of properties we would predict if the collection of particles that mediate the weak force are analogous to the array of mesons that can mediate the nuclear strong force.

Also, the analogy of the nuclear strong force to the weak force suggests that the W and Z bosons, unlike photons and gluons, might be composite particles, rather than being fundamental. (Electroweak unification involves a concept of blending of more fundamental particles to create the W, the Z and the photon, as opposed to a true composite concept.)  This seems like an interesting line of conjecture to extend to see how far one could take it.

And, of course, we've omitted discussion of the Higgs boson, which shows every indication of being basically a part of the electroweak unification scheme that is not closely related to QCD at all, and gravity, which just plain doesn't play well with the Standard Model, but mostly manages to stay out of the way in circumstances where gravity and the Standard Model might clash with each other.

Earliest Evidence of Marijuana Is From Jomon Japan

The earliest evidence of marijuana use by humans (for its hemp fibers) comes from Jomon Japan.

[T]he earliest traces of cannabis in Japan are seeds and woven fibers discovered in the west of the country dating back to the Jomon Period (10,000 BC – 300 BC). Archaeologists suggest that cannabis fibers were used for clothes – as well as for bow strings and fishing lines. These plants were likely cannabis sativa – prized for its strong fibers – a thesis supported by a Japanese prehistoric cave painting which appears to show a tall spindly plant with cannabis’s tell-tale leaves.

Until World War II, it was an important commercial crop in Japan.

This changed after World War II, and Japan now has some of the most strict anti-cannabis laws in the world.

The Selfish Case For Sharing Data

Some scientists horde data, on the theory that this gives them an edge that other scientists in the community lack so that they can publish on something that no one else can publish upon.  Other scientists share data, on the theory that this allows more people to engage with their work and by doing so recognize it.

In academia, the first law of career advancement is publish or perish.  More publications are good. But, academia recognizes superstars based not only upon how many articles one publishes, but how many times those articles are cited by others.

Empirically, if you are a scientist who manages to publish at all (and many people in academia publish very little once they receive tenure), the best way to advance your citation count and thrust yourself into academic superstar status, is to share your data, according to a short preprint examining the question released Sunday, at least in astrophysics, but probably in a much broader array of other disciplines as well.

Overall, making your underlying data available will increase you citation count for a paper by 20% on average.

Waiting For The Next Big Paper

There have been a number of interesting papers on historical genetics and prehistory in the past couple of weeks that I haven't covered because I've been spending lots of days litigating cases in court and in arbitration forums for my clients.

But, a fair amount of interest in the field is devoted to the next big ancient DNA paper which a number of conference announcements discussed by Bell Beaker blogger suggest is coming sometime soon this autumn (in the Northern hemisphere) that will finally shed light on the genetics of the Western European Bell Beaker phenomena.

Of course, it could turn out that the blogging community had read too much into the tea leaves.  But, if such a paper is released, it could resolve a lot of the biggest remaining questions in historical genetics and prehistory.  Western European ancient DNA has been covered much less comprehensively than Central and Eastern Europe in recent autosomal ancient DNA studies, but the archaeology of Western Europe is pretty comprehensive and the technology can now do amazing things with lower quality remains, so there is good reason to be hopeful that the rumored new paper or two will be far more than hype.

Frustratingly, some of these conferences took place in October, but the content of the presentations has nonetheless apparently escaped the Internet's grasp.  But, this does argue against any major breakthrough papers.

This information, in turn, will also shed a lot of light on the question of when, how and from where the Indo-European languages and any predecessor languages arrived in Western Europe, although since pots are not people, new data can only strengthen or weaken arguments about historical linguistics, rather than resolve them definitively.

More On Math Genius Srinivasa Ramanujan

The collected works of the mystical Indian mathematical genius Srinivasa Ramanujan are still yielding valuable mathematical insights almost a century after his death.  The latest insight's involve a class of near counter-examples to Fermat's last theorem (which was subsequently proven to be true in my lifetime, four hundred years after it was proposed).

Razib's Riff On Eurasian Origins

Razib Khan has an extended meditation on the genetic origins of the Eurasians.

Some key points:

(1) Culturally driven punctuated change has been the norm for much of the history of humanity.

(2) One factor driving this population replacement trend has been the fragility of the economic subsistence basis of the conquered people.  Often they have been so fragile and with so little excess that exacting tribute from them and exploiting them as a ruling class has been impossible and instead they were replaced.

(3) The Y-DNA R1a and R1b branches have seen the explosion of the modern sublineages since ca. 3000 BCE, which correspond with the sweeping expansions of these patrilineages into Europe and South Asia, and to a less extent, into the Middle East.

(4) The Neolithic revolution and the subsequent explosion of steppe DNA beyond the steppe has resulted in the integration of populations that were more or less isolated from each other for tens of thousands years created a new homogenized blended population genetic community that had never existed until then.

Put more bluntly, European hunter-gatherers had an extremely different phenotype from the earliest farmers of Europe.  In other words, they were of very distinct races, at least as distinct as Chinese people are from French people today.

One major blending of these two populations gave rise to Early European Farmers to produce a mix much like modern day Sardinians.

Another major blending happened when population genetics from the steppe made its way to Europe sometime in the time frame of the late Copper Age to the early Iron Age to create more or less the modern European phenotype which didn't exist until then.  These steppe people were about half Early European farmer (itself a blend of hunter-gatherers and "basal European farmers", with additional contributions of Ancestral Northern European and Eastern Hunter-Gatherer).  Admixture percentages from substrate populations varied quite a bit in a systemic fashion with more admixture where the food production package brought be the conquering people was less well suited to local conditions.

(5) Y-DNA lineages have a tendency to extend beyond the tightly knit human communities that drive their initial expansions, and also show strong tendencies towards replacement in excess of that seen in autosomal and mitochondrial DNA.

(6) Selective fitness based selection has been ongoing into the modern era.

(7) Razib feels as it most of the puzzle pieces are in place already.  In contrast, I feel as if we have lots of the puzzle pieces together and a good understanding of some regions, but still do not understand the links between the genetic shifts and the historical events that caused them, nearly so well in Western Europe as we do in Eastern Europe and some other areas.