Epipaleolithic Island Colonization

New archaeological finds disclose that many of the islands in the vicinity of the Aegean Sea were colonized by modern humans in the Epipaleolithic era, several thousand years before the Neolithic revolution, and some may have experienced earlier maritime colonizations by archaic hominins such as Neanderthals.

This is consistent with evidence of rather short distance Upper Paleolithic maritime colonizations of Australia and Melanesia (it isn't clear if these were separate colonizations or a single event), of the Philippines, of the Andaman Islands, of the island of Formosa (home to Taiwan), of Japan and some of its neighboring islands, and of crossings of the Strait of Gibraltar.

Indeed, while this is earlier than the Neolithic, these dates are still about 30,000 years or more after modern human Cro-Magnons began to inhabit this region.

But, these colonizations seem to have been rare, with their frequency declining as distances grew greater.  The sea journey that made modern human colonization of Australia and Melanesia seem likely to have been one time only one way journeys, with only one subsequent known instance of interaction (evidence by the introduction of the Dingo to Australia) between then and the Neolithic, which may also have been a one way journey.  Islands, even when accessable by straits easily crossed by boats in the Neolithic and historic eras, are often very distinct genetically from the adjacent mainland (e.g. in the case of Cres Island off the coast of Croatia in Adriatic Sea).

Notably, Madagascar, most of Oceania, and Iceland were not colonized by hominins until the Neolithic era, in the first two cases by Austronesian seafarers, and in the latter case by the Vikings.  Similarly, when Tasmania became isolated by water from mainland Australia as sea levels rose, interactions between those societies, who had lost the requisite maritime technology, ceased leading to technological and culture degredation for the remaining people of Tasmania who were less with a population not sufficiently large to maintain its culture.  The people of the Andaman Islands also seem to have been isolated from the mainland for many thousands of years.

Consistent long distance maritime travel seems to have been nearly non-existent until roughly the Copper Age (and contemporaneous Austronesian journeys), even though irregular and perhaps one way trips in unusually favorable conditions, or much shorter trips where line of sight navigation is possible, may be as old as the Out of Africa event or older.  Alternately, one technology that may be a good fit for regular maritime travel is the development of pottery.

It is a fair assumption that archaic hominins had maritime technologies that were no better than those of Upper Paleolithic modern humans.

To my knowledge, there is no direct archaeological record of pre-Neolithic boats that could have made these crossings at all.

One question that comes to mind, in light of this data, and the indications from genetic evidence that the Epipaleolithic may have seen as much population genetic change in Europe as the Neolithic, is whether there was some sort of behavior modernity shift (perhaps cultural rather than genetic) in the Epipaleolithic on a par with that often attributed to the Upper Paleolithic, even though the existence of a shift to some sort of behavior modernity in the Upper Paleolithic (and even between Neanderthals and modern humans), at all, is seriously disputed by professionals in the field.

Consensus Value For Theta 13 Emerging

As September 26, 2012 paper updates the experimental effort to determine the value of the least well known of the three theta angle parameters in the PMNS matrix that govern neutrino oscillation. In its conclusion, it states:

In the space of ten months five experiments have produced results consistent with a value of sin^2(2 theta13)~ 0.1. As a result it can now be considered "well established" that the Ue3 element of the PMNS matrix is non-zero, with a global level of significance well over the conventional 5 sigma discovery threshold. A summary of these measurements, plus the previous hints from global fits, is provided in FIG 4. With the exception of MINOS, all the experiments described in this talk are expecting to take more data, so the precision on the measured value will almost certainly improve significantly. The divergences between the long-baseline and reactor measurements will now come to the fore, with reactor experiments providing precise measures of [Ue3]^2, while improved measurements from T2K can be used to study CP violation, theta 23, and even the mass hierarchy (via matter effects). The field as a whole is therefore rapidly transitioning from theta13 as an unknown parameter, towards theta 13 as a well-measured input for investigating other parameters.

The experiments shown in Figure 4 are KamLand & Solar, MINOS, T2K, Double Chooz, Daya Bay, and RENO. All of the results have 0.09 within the error bars of as May 2012, which matches the central value of the Daya Bay result from last March, the most precise of the six measurements.

The other two theta parameters of the PMNS matrix (theta 12 and theta 23) are also known with some level of precision, so the only parameter of the PMNS matrix that is not known with any meaningful accuracy at this point is the CP violating parameter of the matrix (zero if there is no CP violation, and non-zero if the neutrino oscillation matrix value, for example, from electron neutrino to tau neutrino and from tau neutrino to electron neutrino are not identical. The corresponding value for the CP violating parameter in the CKM matrix which applies to quark weak force flavor transitions in non-zero.

For theorists this development signals an imminent transition from the period of time in which mere pro forma estimates of the PMNS parameters such as the tribimaximal values will be replaced with genuine experimental values for each of the parameters of the PMNS matrix.

Background

There are a number of parameters of the Standard Model.

Some Standard Model parameters are considered "exact" or not treated as "constants" at all, such as the spin-1/2 of Standard Model fermions, the spin-1 of photons, W bosons, Z bosons and gluons, the spin-0 (scalar rather than pseudo-scalar) of the Higgs boson, the charges of the fundamental particles (+/- 2/3 for up type quarks and anti-quarks, +/- 1/3 for down type quarks and antiquarks, +/- 1 for charged leptons and W bosons, and 0 for neutrinos, photons, Z bosons and gluons), the three QCD colors, the three generations of fermions, the precisely eight types of gluons, the existence of left handed and right handed version of all fermions except neutrinos (which come only in left handed particles and right handed antiparticles), the zero masses of photons and gluons, and the assumption that there are exactly four dimensions of space-time. Also in this category are the exact forms of the Standard Model equations and conservation laws (e.g. baryon and lepton number conservation, matter-energy conservation, charge conservation, etc.).

There are other constants in the Standard Model that are measured. Specifically, the masses of each of the twelve types of fermions (with their antiparticles having precisely the same masses), the mass of the W boson, the mass of the Z boson, the mass of the Higgs boson, the coupling constants for the electromagnetic, weak and strong forces, four parameters in the CKM matrix that applies to weak force mixing of quarks, the four parameters of the PMNS matrix that applies to the weak force mixing of leptons, and two "beta function" constants that describe the running of each of the three coupling constants. There is in addition, one constant which is experimentally indistinguishable from zero and generally assumed to be zero in the Standard Model, but not otherwise disruptive to the Standard Model if it is small but non-zero, which relates to CP violation in the strong force. (There are also theoretically expected values of the Higgs boson coupling constants in the Standard Model, but those have not yet been confirmed in detail experimentally.)

A relatively minor variant on the Standard Model in which neutrinos are Majorana, rather than Dirac, in nature, would add two constants to the PMNS matrix and up to three more mass constants for neutrinos (to reflect their Majorana and Dirac mass components respectively). This would also alter the form of one of the "exact" Standard Model conservation laws (from separate baryon number and lpeton conservation to B-L number conservation). Two other experimentally values assumed to be zero in the Standard Model and have measured values consistent with zero, are the proton decay rate and the neutrinoless double beta decay rate for select radioactive atomic isotypes (which is a measure of lepton number violation frequency).

One of the great unsolved mysteries of physics is to discern if there is some means by which the experimentally measured fifteen masses, nine coupling strength constants, and eight mixing matrix parameters can be derived from first principles using some smaller number of fundamental constants.

There is good reason to think that there is some unknown structure or formula that relates these quantitites in a manner that could also explain unsolved problems of fundamental physics like the hierarchy problem (which relates to the way that a large number of very large terms (some not known with precision) that go into calculating the Higgs boson mass from first principles mysteriously cancel out to produce the relatively modest observed value of the quantity.

One of the main barriers to this enterprise is that the accuracy of the estimates of quite a few of the parameters, such as the masses of the five quarks other than the top quark (which can be observed directly due to quark confinement and also have very theory dependent estimation protocols), the three neutrino masses (which are hard to measure because neutrinos interact only via the weak force and are tiny), the beta function constants (which are sensitive to thinny measured very high energy data points), the CP violating term of the PMNS matrix (lower case delta), and the three theta parameters of the PMNS matrix are not known to sufficient levels of precision to exclude a wide variety of possibly spurious, empirically observed numerological coincidences of the values that are consistent with experiment to within the existing margins of error in measuring them.

In contrast, the masses of the top quark, of the charged leptons, of the W boson, of the Z boson, and increasingly of the Higgs boson, as well as all four of the CKM matrix parameters, and the basic coupling constant values of the strong, weak, and electromagnetic forces before adjusting for the running with different energy levels, are all known to considerable precision, and the masses and other properties of many composite particles (e.g. protons, neutrons, atoms, and many classes of exotic mesons and baryons) have also been measured experimentally to a high level of precision. Likewise, Koide's rule provides a very precise empirical relationship between the masses of the charged leptons (although without any known basis for their relationship).

Within the realm of fundamental physics, but not stictly speaking part of the Standard Model, are several other fundamental physical constants known to some reasonable level of precision, most notably Planck's constant, the speed of light, the gravitational constant, the cosmological constant, Hubble's constant (and relatedly, the age of the universe), the measured proportions of "dark matter" in the universe, and Milgrom's MOND constant a0 which accurately describes the effective dark matter distribution at the galactic scale with a single parameter (something not achieved by any of the prevailing dark matter models).

Many quantum gravity theories that could be integrated with the Standard Model (without forming a true grand unified theory) have at least one or two more additional constants related to quantum gravity effects and modification of beta functions to reflect quantum gravity effects at high energies. For example, many such models have a minimal scale of space-time that is fundamental.

400 Posts

I'm pausing just a moment to observe that a week short of eighteen months after starting this blog there have been 400 posts. Thank you for reading this blog. Feel free to live any general comments about the subjects covered by this blog in the past, or interesting future subjects to cover, in the comments.

Some topics such as military technology, economic issues related to science and technology, mental health, neuroscience, psychiatry, and public health are matters that I primarily cover in this blog's sister blog, "Wash Park Prophet" because they have many social science and political dimensions to them. This blog primarily covers physical sciences developments without direct economic implications, prehistory, ancient history, mathematics, and related developments, particularly in the area of population genetics. But, any area where science and scholarship are developing in a way usually irrelevant to short to medium term public policy is appropriate for coverage here.

New Data Still Favors SM Higgs and SM Generally

New data, although not as much as one might hope for, from the LHC, since it made the announcement that it had discovered the Higgs boson, favors the conclusion that the particle discovered is the Higgs boson of the Standard Model, rather than having properties that would suggest new physics.

Details Of The Evidence That The Higgs Boson Has Standard Model Properties

One set of early results which had earlier shown a somewhat significant difference from the Standard Model expectation (the tau-tau decay channel), has produced outcomes closer to the Standard Model expectation now that the data set has gotten larger. A deficit in the number of events observed of that type at the LHC in the earlier results appears to have been just a statistical fluke.

"They also claim to rule out (at 2.5 sigma) the hypothesis that this is a pseudoscalar rather than scalar." A pseudoscalar Higgs boson would suggest that it might be a composite rather than fundamental particle, since many spin-0 mesons (two quark composite particles) are pseudoscalar rather than scalar. (Explaining the difference between the two would take more time than I have available for this post.)

New data is not available for the diphoton channel (aka gamma-gamma) or the ZZ channel, which had shown statistical excesses in earlier results.

Rumor has it that these results were delayed, despite showing less of an excess from the Standard Model expectation, and thus more strongly confirming the Standard Model, because the inferred masses of the Higgs boson in the data from the different channels isn't the same and the theorists suspect that rather than being a sign of new physics (or even more than one neutral Higgs boson, each of which has similar but not identical masses) that instead this is a product of some sort of systemmic error in their calculations or experimental setup.

The LHC scientists don't want to create all sorts of buzz about new physics only to have it evaporate when a stupid mistake in collecting or analyzing the data is discovered a few months later, the way that it was in the superluminal neutrino fiasco at the Opera experiment a few months ago. But, the end result of the Kyoto meeting data dump from the LHC on the Higgs boson is that the dog that didn't bark turned out to be the bigger subject of discussion that the data that was actually revealed.

SUSY Parameter Space Continues To Narrow

Meanwhile, the new data continues to corner the viable supersymmetry theory parameter space as new LHC results continue to precisely fit the Standard Model expectations to greater levels of precision. There are fewer gaps into which the "god of the gaps" SUSY theories can add insight. Potential supersymmetric particles have been excluded to ever higher masses, and other parameters of the SUSY model like "tan beta" have also been materially constrained.

The LHC will never, even after its run is completed, be able to exclude all theoretically possible SUSY theories. But, it is coming close to excluding all of the SUSY models that SUSY proponents were advocating until just a few years ago (call them "just around the corner" models), and more importantly, is coming close to excluding most of the SUSY models that are natural solutions to the Standard Model features that SUSY models sought to provide when it was invented.

For example, a year ago, a leading SUSY advocate was discussing models with 600 GeV mass gluino superpartners. "This week ATLAS reports a new gluino mass limit of 1.24 TeV." As one physicist who continues to write papers advancing possible SUSY models describes the situation:

The bottom line is simple: neither CMS nor ATLAS sees any significant deviation from what is predicted by the Standard Model. And this now kills off another bunch of variants of many different speculative ideas. The details are extremely complicated to describe, but essentially, what’s dead is any theory variant that leads to many proton-proton collisions containing

■two or more top quark/anti-quark pairs
■multiple W and Z particles
■two or more as-yet unknown moderately heavy particles that often decay to muons, electrons and/or their anti-particles
■new moderately heavy particles that decay to many tau leptons
and probably a few others I’m forgetting.

Generically, the surviving SUSY models have heavier superpartners, are less natural, and are butting up against other problems like a failure to observe neutrinoless double beta decay at the levels expected in models with heavy superpartners.

Were Classic SW Asian Neanderthals Admixed?

John Hawks (whom I am fated to miss every time he is in Denver to give a talk), has published a timely new survey of the state of knowledge in multiple disciplines regarding Neanderthals in light of new scientific developments.

The New Genetic Developments

The most profound development has been the sequencing of ancient DNA samples. He notes, in a decidedly glass half empty response to a near miracle of modern technology that "the genetic data from Neandertal skeletal remains are sparse, with fewer than two dozen mtDNA sequences (Dalen et al., 2012), and only six specimens with substantial nuclear DNA information (Green et al., 2010)." We also have a few nuclear genomes from the Denisova Cave in the Altai Mountain area of Russia.

Genetic data collected from modern populations have disclosed that all ancestrally non-African modern populations show a low percentage of Neanderthal admixture that can be confirmed by direct comparison with the ancient genomes. Likewise, Papuans, Australian aborigines, and populations derived from them, have significant Denisovan admixture in addition to their Neanderthal admixture that can be confirmed by direct comparison to ancient Denisovan genomes. A few of the oldest ancient nuclear DNA samples from Europe, most recently in the case of Otzi the Iceman, have likewise revealed distinctive Neanderthal DNA admixture patterns.

We have no ancient genomes to use as comparison samples from Africa. But, the same statistical methods that suggested that there might be ancient hominin ancestry where direct comparison later confirmed Neanderthal and Denisova admixture in modern genomes has also detected traces of ancient hominin admixture with at least one or two ancient hominin species in Africa that survives today in some Central African Pygmies and Southern African Khoi-san peoples, who are sometimes described as "Paleoafrican" because their uniparental genetic lineages are more basal in the phylogeny of modern human genetics than any others on earth.

The New Archaelogical Developments

There has also been a steady stream of new archaeological evidence from new excavations. The most notable of these has been discovery of a new ancient hominin species, Homo Florenesis sometimes called "Hobbits," over the objections of J.R.R. Tolkien estate, on the island of Flores in Indonesia, very close to the place where Denosivan genetic admixture starts to appear in indigenous populations.

Other important finds have been the discovery of the first post-Toba explosion, pre-Australian and Papuan settlement modern human remains in a cave in the Southeast Asia highland of Zomia, a correction to the dating of the youngest Homo Erectus specimen in Indonesia making it a pre-Toba eruption specimen, the discovery of Neanderthal remains not far from the Denisova Cave, clarification of the sequencing and dating of Neanderthal occupations and subsequent modern human occupations of sites in Europe, and the discovery of the use of a few technological techniques by Neanderthals in Europe that had not previously been documented.

Among other things, the improved dating has shown the arrival of modern humans in Europe to have been a more rapid colonization than had previously been assumed. This has also permitted a more nuanced analysis of the relationship between the arrival of modern humans in Europe, the decline of Neanderthals in Europe, and contemporaneous major volcanic eruptions and climate developments.

New archaeological excavations in Arabia that have just started to become available to member of the public have pushed back the earlier orthodoxy about when modern humans emerged from Africa finding distinctively modern human relics in inland Arabia more than 100,000 years ago with a clear affinity to contemporaneous Nuba complex modern human relics in Africa.

Hawks On Neanderthal Types

Much of Hawks paper simply summarizes some of these new developments, but the really powerful addition that his paper makes is in its revisiting of physical anthropology subtyping of Neanderthals skeletal remains that had culminated in a paper by Howell in 1957. The remainder of the paper then begins to fit these subtypes into a narrative in the context of the other evidence.

Howell distinguished Neanderthal remains by era, roughly speaking those before and after 100,000 years ago (the former being "early" and the latter "classical") and by region, with Southwest Asian instances being distinct from those to the North on a North-South axis, and other distinctions emerging in his study and later ones on an East-West axis in Eurasia.

Hawks makes this key observation on page 6 of the paper:

A problematic aspect of the idea of Levantine Neandertals is that the very features that distinguish them from European Neandertals tend to align them with modern humans. For example, the Amud skeleton has stature and limb proportions that set it apart from European Neandertals, but that fall within the range of variability of the Skhul and Qafzeh skeletal remains. Trinkaus (1995) considered the Near East, including Shanidar and the Levantine samples, to include two forms of hominins: “late archaic” and “modern” forms. He argued that the late archaic forms in the Near East have no close connection to European Neandertals, and that similar features reflect mosaicism or generalized archaic morphology in both evolving populations.

Several workers after Howell added the concept of a north-south axis of Neandertal diversification within Europe. Rosas and colleagues (2006) noted that southern Neandertals tend to have increased heights of the lower face and broader faces than the northern sample of Neandertals within Europe. Because the line separating north and south must run along the very long east-west axis of Europe, there are many possible ways to divide the continent into northern and southern samples.

Connecting The Dots

Hawks pulls his punches and refrains from sweeping conclusions, ending his paper with the simple observation that the genetic evidence and archaeological evidence alike indicate that there were several distinct subtypes of Neanderthals in space and time whose categorization has still to be worked out.

But, being the fool who rushes in where angels fear to tread, it isn't hard for me or anyone else familiar with the data to connect the dots.

The emerging genetic evidence suggests that modern human-Neanderthal hybridization probably took place after the Out of Africa event but well before the Upper Paleolithic revolution with Southwest Asia as a prime candidate for the location of this event, as that is where first contact must have taken place and the modern human range did not extend to Europe or further than India for much of that time period.

The obvious conclusion to jump to would be that the similarity of "classic" era Southwest Asian physical skeletal remains to modern humans, relative to Neanderthals elsewhere and from earlier eras, would be that these similarities are due to the impact of modern human-Neanderthal admixture on the Neanderthal populations of the Southwest Asia.

Likewise, an obvious conclusion to jump to that few professional anthropologists have committed to stating forthrightly, is that the post-Mousterian technological cultures of the Neanderthals may have been the product of the increased capabilities of admixed Neanderthals in those communities relative to their pure Neanderthal predecessor.

Hawks has instead advanced the hypothesis that Neanderthals were more fully within the range of modern human variation than they are given credit for being and were more human-like in general than previously assumed. His public comments lean towards the notion that Neanderthals were more of a subspecies of Homo Sapiens than a separate hominin species.

But, personally, I am more inclined to interpret the evidence of behavioral modernity and morphological similarity between Neanderthals and modern humans, not as much as a sign of convergent evolution or close evolutionary relationships, as it is a manifestation of highly influential admixture with modern humans. Indeed, in Southwest Asia and toward the end of the period of Neanderthal and modern human cohabitation of Europe, Neanderthals may have been more admixed with us than we were with them.

Reference

John Hawks, "Dynamics of genetic and morphological variability within Neanderthals" 90 Journal of Anthropological Sciences 1-17 (2012).

Dysentery, A Less Well Known Historical Epidemic

Dysentery epidemics in the 1700s and 1800s in Sweden, which are well documented with contemporaneous written records, were much more serious than are commonly know, accounting for 90% of deaths in some regions when the epidemics struck.

Many historians have described dysentery as a regularly recurring and not very serious disease. Cholera and smallpox are often described as the most devastating epidemic diseases of that era. But [Helene] Castenbrandt's results beg to differ.

"My study points to dysentery as very epidemic in nature. The disease struck communities extremely hard at times. It flared up quite irregularly and the patterns of transmission differed from one outbreak to the next."

Using Jönköping County as an example, the study clearly shows the vast differences in dysentery mortality within the same county. The pattern of transmission for the three most severe outbreaks in 1773, 1808 and 1857 shows that although the disease spread across almost the entire county, there were some clusters with extremely high mortality. However, the hardest hit parts of the county varied.

The [doctoral] thesis [from the University of Gothenburg] also analyses the reasons behind the presence and disappearance of the disease. The results point to complex links between possible explanations such as sanitary conditions and population concentrations for example in connection with wars.

An understanding of the lessons learned in Europe during this forgotten era could inform modern efforts to address similar issues in the developing world in a manner that is not overwhelmed by donor nation concerns rooted in their own contemporary economic politics rather than the issues that were important historically when the donor nations dealt with similiar issues themselves.

The Lost Civilizations Of The Wet Sahara

An image illustrating the location and scale of the Saharan Megalakes (via the Linear Population Model Blog).

There were several huge freshwater lakes in what is now the Sahara desert in Southern Libya that dried up about 3,000 years ago (Lake Chad was also much larger and the surrounding regions were much more lush in this era, particularly in highland areas).

At their peak, these lakes supported food producing, tool making civilizations that left their rock art behind. In this era, the Sahara desert region that now forms a barrier between North Africa and the rest of the Continent was instead a hub of modern human activity.

The past few years have produced a considerable body of scholarly work that describes what was going on in Saharan North Africa from the early Neolithic era through what was in Europe the Bronze Age, which would have been impossible if naive extrapolations of current climate conditions back to that era were accurate. This newly discovered chapter of North African prehistory has the potential to inform a greatly revised understanding of the historical roots of the modern African cultures of North Africa, West Africa and East Africa.

Marnie Dunsmore's blog, Linear Population Model, has had a number of very solid recent posts on North African pre-history and genetics that explore these points.

Posts here, here and here provide the foundational paleoclimate evidence that has been developed about the Holocene Climate Optimum in the Sahara. Then, one links a lithic chronology of that period in the region at another blog (Two posts link recent published articles on the same subject). There is a post that references an scholarly article linking archaeological relic finds to the wet Sahara era and the cultures implicated in them. Three more posts fit Saharan rock art into this context (also here).

An article identifying possible refugia of African Savannah herd animals based upon genetic evidence and interpreted in light of paleoclimatic conditions is identififed in another recent post.

There is now a solid periodization of several successive well defined archaeological cultures of the Central Sahara, in places where one wouldn't think to look for human relics and remains at all, that also shed light, for example, on the chronology of and process by which dairying, and more generally food production via herding domesticated animals, arrived in North Africa. Understanding this chronology is also absolutely essential to piecing together the origins of Africa's major linguistic families and the sources of its modern ethnic groups.

Some Uniparental Genetics Of North Africa Posts

More recent posts at Linear Population Model have also had discussions relevant to North African prehistory in light of human population genetic evidence.

One concerns the possibility that mtDNA haplogroup H1 arrived in North Africa from Southern Europe in the Epipaleolithic possibly in association with Y-DNA haplogroup R1b-V88, in light of a 2010 PLOS paper on the subject. I am inclined to give credit to the 2010 paper's suggestion of an Iberian origin for H1 that may have been pre-Neolithic (something that is also likely the case of mtDNA haplogroup V). But, I have serious doubts about the importance as a route of prehistoric migration (in both directions and by both humans and other fauna) that Marnie has attributed to the Straight of Sicily.

I also am inclined to think that the R1b-V88 is to closely linked to the linguistically Chadic population and its near geographic neighbors, who are probably relatively recent arrivals on the African scene (my best guess from the published work would be 5,000 BCE to 3,000 BCE), to have a strong association with mtDNA H1. I am also inclined, given its phylogenetic relationship to the R1b clades found in Western Europe in general, and Iberia in particular, to think that R1b-V88 has African origins that derive from Southwestern rather than Southeastern Europe.

Another post has a nice vigorous discussion of the back migration of mtDNA haplogroups M1 and U6 to Africa and their subsequent expansions, as compared to the modal European mtDNA haplogroup, U5. Some of the key issues are which of the North African archaelogical cultures to associate these mtDNA haplogroups with; the issues involved in determining if these are pre-Last Glacial Maximum ca. 20,000 years ago (and hence associated with an older archaeological culture in North Africa), or post-LGM (and associated with a more recent archaeological culture), are quite technical and not salient enough to the big prehistory issues I care most about right now to inspire me to really closely examine the arguments on this point.

Neanderthal Admixture Revisited

The conclusion of the lastest (open access) PLOS paper on the circumstances involved in a Neanderthal admixture with modern humans states:

The date of 37,000–86,000 years BP [for Neanderthal admixture/genetic overlap with modern humans as measured by linkage disequalibrium genetic methods] is too recent to be consistent with the “ancient African population structure” scenario, and strongly supports the hypothesis that at least some of the signal of Neandertals being more closely related to non-Africans than to Africans is due to recent gene flow. These results are concordant with a recent paper by Yang et al that analyzed joint allele frequency spectra in Africans, non-Africans and Neandertals, to reject the ancient structure scenario.

After the present paper was accepted, Eriksson and Manica showed, using an Approximate Bayesian Computation approach, that models of ancient substructure can produce a signal of Neandertals sharing more derived alleles with non-Africans than with Africans (that is, they can account for the observation that D-statistics are significantly different from zero). The same observation was made in our earlier papers on the draft Neandertal and Denisovan genomes where we introduced D-statistics. However, the new statistics we focus on here as well as the statistics focused on by Yang et al show that ancient structure alone cannot explain these signals.

One possibility that we have not ruled out is that both ancient structure and gene flow occurred in the history of non-Africans. In the simulations reported in Table 1, we show that in this scenario, the ancient structure will tend to make the date estimate older than the truth but by not more than 15%, so that the date of 37,000–86,000 should still provide a valid bound while the less conservative estimate of 47,000–65,000 years should be interpreted as an upper bound on the date of gene flow.

Further, we have not been able to differentiate amongst variants of the recent gene flow scenario: a single episode or multiple episodes of gene flow or continuous gene flow over an extended period of time. Our date has a clear interpretation as the time of last gene exchange under a scenario of a single instantaneous gene flow event. In the other scenarios, the date is expected to represent an average over the times of gene flow and should be interpreted as an upper bound on the time of last gene exchange.

While recent gene flow from Neandertals into the ancestors of modern non-Africans is a parsimonious model that is consistent with our results, our analysis cannot reject the possibility that gene flow did not involve Neandertals themselves, but instead populations that were more closely related to Neandertals than any extant populations are today. Thus, the date should be interpreted as the last period of time when genetic material from Neandertals or an archaic population related to Neandertals entered modern humans.

Genetic analyses by themselves offer no indication of where gene flow may have occurred geographically. However, the date in conjunction with the archaeological evidence suggests that the two populations likely met somewhere in Western Eurasia. An attractive hypothesis is the Middle East, where archaeological and fossil evidence indicate that modern humans appeared before 100,000 years ago (as reflected by the modern human remains in Skhul and Qafzeh caves), Neandertals expanded around 70,000 years ago (as reflected for example by the Neandertal remains at Tabun Cave), and modern humans re-appeared around 50,000 years ago.

Our genetic date estimates, which have a mostly likely range of 47,000–65,000 years ago (and are confidently below 86,000 years ago), are too recent to be consistent with the appearance of the first fossil evidence of modern humans outside of Africa—that is, our date makes it unlikely that the Neandertal genetic material in modern humans today could arise exclusively due to the gene flow involving the Skhul/Qafzeh modern humans—and instead point to gene flow in a more recent period, possibly when modern humans carrying Upper Paleolithic technologies expanded out of Africa.

Note: I include almost the entire conclusion rather than select excerpts, despite copyright to capture numerous important qualifiers to the conclusion in the original and feel that this constitutes fair use particularly in light of the fact that this is an open access, basic science publication.

LD methods of dating are far less controversial than mutation rate dates. They rely on some basic and well established features of the recombination process at each generation, and essentially measure how well shuffled SNPs are as a result of that process, rather than the number of mutations against some baseline found in a genome.

This study, together with other recent research, establishes that:

1. Neanderthal admixture with Eurasian modern humans (or admixture with archaic hominins more closely related to Neanderthals than to modern humans or Denisovans) did take place sometime in the Middle Stone Age or Upper Paleolithic era, rather than simply be an artifact of ancient population structure, even though there may be some contribution from ancient population structure.

It is clear from ancient DNA and other evidence that there was indeed significant population structure among both Neanderthals and modern humans in the Middle Stone Age and Upper Paleolithic. Ancient DNA shows some level of regional differentiation in Neanderthal genetics. Similarly, Eurasian uniparental mtDNA and Y-DNA phylogenies are derived from only a small subset of Africa's population genetic diversity (unsurpisingly, the subset likely to have origins in the vicinity of the geographic areas in Africa where modern humans first left that continent).

It is not at all clear that Eurasian modern humans had much internal population structure prior to a schism between West Eurasian and East Eurasian populations, although uniparental genetic phylogenies are not inconsistent with the possibility that there could have been two or three subgroups of Eurasians with significant population structure.

It is also not clear how much of the current internal genetic diversity in West Eurasians and in East Eurasians that is not clearly attributable to mutations arising in situ in the first populations present in a geographic area, was present from the start, as opposed to arising from subsequent wave of migration. A material part of the genetic diversity in modern populations, at least, is derived from later migration waves and was not present when the first modern humans arrived at particular location in Europe and Asia. Likewise, some of the genetic diversity present in the earliest Eurasian populations must have involved genetic features found only in populations that have since gone extinct.

2. Most of the admixture evidence in modern humans alive today took place before modern humans arrived in Europe, but after they left Africa.

3. At least some of the admixture took place at a time closer to an "Out of Arabia" date than to an "Out of Africa" date given the increasing archaeological evidence for an Out of Africa date before 100kya. (No one seriously argues that modern Eurasians are descendants predominantly from initial Out of Africa migrants via Spain or Italy, rather than via Israel or southern Arabia.)

4. The study does not resolve whether admixture happened before, after, or both before and after, the ancestors of modern Eurasians split into West Eurasian and East Eurasian populations.

There is relatively little overlap between the Neanderthal SNPs found in West Eurasians and the Neanderthal SNPs found in East Eurasians, suggesting that either parallel admixture events as the source of at least some admixture in these populations, or founder effects at the time of the West Eurasian-East Eurasian schism prior to Neanderthal admixture reaching a point of fixation are the most likely source of this distinction. This schism is nearly complete no further east than the India-Burma border.

5. Neither this study, nor previous ones, provide much insight into whether admixture was a punctuated event or a gradual process over millenia of co-existence. The absolute number of admixture events and the effective population size of the early Eurasians at the time of Neanderthal admixture are not very tightly constrained. We do know that there is no Neanderthal mtDNA or Y-DNA in any modern human now living (out of more than a hundred thousand people tested in a way that oversamples potentially significant outliers) or in any ancient DNA from a modern human. We do know that East Eurasian Neanderthal admixture preceded Denisovan admixture in the proto-populations that gave rise to Papuans and aboriginal Australians.

6. There is considerable reason to believe from ancient DNA evidence and circumstantial evidence that indigeneous European hunter-gatherer populations (and populations with large demographic contributions from these populations that transitioned in food production methods) had much higher levels of Neanderthal admixture than modern European or Asian populations, as a result of additional Neanderthal admixture taking place upon arrival in Europe. This persisted in parts of Europe at least until the Copper age (ca. 3500 BCE).

The most plausible explanation for why this is no longer the case is that subsequent waves of migration after Neanderthals went extinct a little less than 30,000 years ago, by people who lacked this elevated level of Neanderthal admixture into Europe because their ancestors were from places where Neanderthals ceased to be present much earlier, have diluted the admixture levels seen in modern European populations. This suggests that there were very significant demic contributions from outside Europe (or at least from the European far fringe) to European population genetics within the last 5,500 years or so.

Source: Sriram Sankararaman, Nick Patterson, Heng Li, Svante Pääbo, David Reich
"The Date of Interbreeding between Neandertals and Modern Humans," PLOS Genetics, October 2012 link.

Orion's Nebula Probably Home To Black Hole

The Great Orion Nebula, in the constellation Orion, which is about 1000 light years away from Earth (within the Milky Way galaxy and closer than the galaxy's central black hole), is probably home to the closest black hole to our solar system. Some of the stars meaningfully influenced by this possible black hole can be seen with binoculars from Earth and have been known since Galileo's time almost four hundred years ago. More stars in the Nebula can be seen with a decent telescope.

Negative Probabilities

Many, if not all, of the fundamental and irreducible differences between quantum physics and classical physics, which makes phenomena that would be impossible in any classical physical model possible in quantum physics, boil down to the presence of negative probabilities in the quantum physics formulas. Negative probabilities, a concept that is hard to even define or conceptualize in the abstract, are axiomatically forbidden in classical physics.

The Albert's Socks Illustration Of Negative Probabilities

A recent blog post by Johannes Koelman on negative probabilities in quantum mechanics is the most lucid explanation of the concept aimed at a layman that I have ever seen. An academic paper made available in preprint form the same week covers much of the same territory in a manner that is more mathematically rigorous and that explores two subtypes of the concept.

The post uses the analogy of "Albert's Socks", involving a mysterious three drawer by three drawer sock chest in which only one row, or one column of drawers may be opened on any given day (with socks redistributed between days). Any given drawer may have either one sock or no sock. Any row will always have either zero or two socks with equal probability. Any column will always have one sock.

This seems to be contradictory. If every column has an odd number of socks, there must always be a odd number of socks in the chest. If every row has an even number of socks, there must always be an even number of socks in the chest. But, a set of rules that involve negative probabilities can fit the data.

A probability function that produces this outcome has ten possible states. Nine states (each of which is assigned a probability of 1/6) have every possible way to have two socks in a row. One more state has no socks in the chest at all (which is assigned a probability of negative 1/2). By adding up all ten states for any given row, or for any given column, one can get the probability that is observed when any given row or column is measured.

The state with negative probability suppresses a particular subset of outcomes of the other "realistic" outcomes (whose combined probabilities exceed one in isolation whenever negative probabilities come into play) in a particular, well defined way.

Since it is impossible to view all of the drawers at once, an observer can never know which of the ten possible states came up when a particular column or row was observed, and the negative probability state itself is never observed, for example, when an observe chooses to look at a column.

In general, negative probabilities are only possible in systems (1) where only part of the system is observed at once (Heisenberg's uncertainty principle decrees that this cosmic censorship principle is necessarily true in all real world quantum mechanical systems), (2) where the sum of all probabilities of given states, positive and negative sum to one, and (3) all observable probabilities are non-negative.

This basically parallels the notion of complex numbers, which often are used in intermediate steps in applied applications, but in the real world, arising in formulas where the observable outcomes are always real valued rather than complex.

Probability Amplitudes Methods Compared

The alternative way of reaching the same result without the radical concept of negative probabilities involves probability amplitudes, in which probabilities are represented as vector quantities (i.e. arrows in space), rather than as scalar quantities (i.e. simple numbers), and the final probability is the square of the magnitude of the the sum of the probability amplitude vectors for all of the possibilities combined. The best layman oriented explanation of that mathematically equivalent alternative to using negative probabilities is by Richard Feynman as a part of his transcribed series of four lectures entitled "QED" (for quantum electrodynamics, which he was pivotal in formulating in terms of probability amplitudes).

Thinking of negative probabilities that contribute to an outcome as probabilities oriented in different directions in some sort of phase space is easier to get one's head around than trying to understand the meaning of individual negative probabilities in isolation (and in much the same way, conceptualizing complex numbers as vector rather than scalar quantities that are opposed in different directions on a complex plane is much easier than simply trying to understand the square root of negative one in isolation).

The probability amplitude method makes the condition that all observed probabilities are non-negative be non-negative when the formulas are applied appear obviously and trivally true. This is reassuring, because it is not easy to state the conditions that must be present once negative probabilities are introduced, for this condition to hold when an algebraic as opposed to a geometric description of the concept is used.

But, it is far less obvious when using probability amplitudes that the sum of all of the probabilities for every possible outcome in a given application really do sum to exactly one, which is often trivial in an algebraic approach using negative probabilities.

Also, an algebraic approach using negative probabilties makes the point that there is a deep and fundamental connection between the fact that not of all a system is observable at once (even in theory) and the phenomena (like quantum tunnelling) that are possible in quantum electrodyamics (and quantum physics generally) which would be impossible using Maxwell's equations of electromagnetism (and in purely classical physics generally). This deep and fundamental connection is not nearly so self-evident when probability amplitudes are used.

The way that probability amplitudes dovetail nicely with the notion of complex numbers likewise being vector rather than scalar quantities that are manipulated accordingly, also provides a natural segue between complex numbers and related notions like quaternions, which have a very natural vector representation that generalizes transparently from the complex number concept even though the abstract algebra generalization of complex numbers is rather daunting.

Other Applications

Because the concepts of probability amplitudes and negative probabilities are so fundamentally necessary in every day, routine quantum mechanics, the mathematics involved are quite well developed and the issues are quite well understood.

Of course, like any other kind of mathematical idea, there is no good reason that a concept like this that has applications in one context might not have applications in another totally unrelated field.

To my knowledge, this hasn't been done in any field outside of the physical sciences in any serious way. But, the Albert's Socks analogy suggests one place where it might have an application, which is in describing public opinion, for example, in politics.

One of the odd features of public opinion that comes up a lot in the political theory of voting is that political preferences are not necessarily transitive. The fact that a majority of people prefer Quinn to Erin, and that a majority of people prefer Erin to Dave, does not in fact necessarily imply that a majority of people prefer Quinn to Dave.

This reality is known as Arrow's Paradox (after economist Kenneth Arrow), and is often stated as follows:

[W]hen voters have three or more distinct alternatives (options), no rank order voting system can convert the ranked preferences of individuals into a community-wide (complete and transitive) ranking while also meeting a specific set of criteria. These criteria are called unrestricted domain, non-dictatorship, Pareto efficiency, and independence of irrelevant alternatives. . . . Although Arrow's theorem is a mathematical result, it is often expressed in a non-mathematical way with a statement such as "No voting method is fair," "Every ranked voting method is flawed," . . . These statements are simplifications of Arrow's result which are not universally considered to be true. . . .what Arrow's theorem really shows is that any majority-wins voting system is a non-trivial game, and that game theory should be used to predict the outcome of most voting mechanisms. This could be seen as a discouraging result, because a game need not have efficient equilibria, e.g., a ballot could result in an alternative nobody really wanted in the first place, yet everybody voted for.

(Note that Arrow's paradox merely says that no voting method is fair for all possible distributions of preferences - the fortunate reality is that most of the time there is a single consistent ranking but that there are gray area cases where ranking preferences cannot be done consistently in any particular system.)

Given that Arrow's paradox involve circumstances where incomplete information gathering about the total data set at any given time can produce seemingly inconsistent outcomes, a negative probability framework might have application to these kinds of problems in the social sciences and provide insight into their deeper structure.

The subdiscipline of economics where Arrow's paradox and related theories come into play are mostly related to how to maximize utility for a group of people even though one person's utility can't strictly and rigorously be equated with another person's utility, is called "welfare economics", not because it is about welfare programs, but because it is about the general welfare of the members of the community at large.

One also might imagine that the use of negative probability outcomes might be helpful in game theory to identify circumstances and conditions in which using seemingly inconsistent strategies makes sense, depending upon the manner in which one part of a larger problem presents itself to a decision maker. Negative probabilities, also known as quasi-probabilities are also used in mathematical finance and derivative pricing.

In What Circumstances Will New Physics Matter?

New Physics Have Not Yet Been Found

The bottom line from the Large Hadron Collider, so far, has been that (1) a new boson that is a good fit so far for the Standard Model Higgs Boson has been discovered and (2) all of the data gathered so far, which probes up to the 1 TeV energy scale, confirms an unmodified Standard Model prediction.

In other words, up to the 1 TeV energy scale, the has been no discovery of new, beyond the Standard Model physics at the LHC.

Of course, as theorists are quick to remind us, it is always possible that beyond the Standard Model physics could appear at energy scales greater than those probed so far. Maybe there aren't any effects that can be reliably discerned until one reaches the 5 TeV energy scale, for example.

The Standard Model As A Low Energy Effective Theory

Even many strong proponents of the Standard Model who are deeply skeptical of the leading beyond the Standard Model theories circulating today will often acknowledge that they too believe that the Standard Model is more likely to be a low energy effective theory. The Standard Model may simply capture the "low energy" behavior of the true, deeper, ultimate laws of nature that applicable in all circumstances. In these context, "low energy" means the kind of situations that we can observe in our laboratories on Earth which are pretty feeble compared to the awesome scale in time, space and matter-energy involved to the universe itself.

The Particle Physics Desert

The Standard Model's resiliance at high energies owes quite a bit to the concept of "running constants." It has formulas that explain how the strength of the three forces it describes vary with the energy scale of the interaction. Those three forces are the electromagnetic force, the strong nuclear force that holds quarks together in protons and neutrons which also holds atomic nuclei together, and the weak nuclear force that brings about the decay of heavy atoms and exotic subatomic particles.

If you do the math, adjusting for special relativity, but not any general relativistic or quantum gravity effects (which is what the Standard Model does), these forces become almost identicial in strength at a point known as the Grand Unification Theory scale, which appears to be a "natural" place to look for new physics. The Grand Unification Theory (GUT) scale is at about 10^13 TeV.

A few orders of magnitude greater than that, and also a strong candidate for new physics is the Planck scale (10^16 TeV), derived from combining fundamental physical constants in a way that produces a set of man made arbitrary units (they are called "natural units" but I've overused that term in this post and want to be clear about the intended meaning). At energy scales greater than the Planck scale, the Heisenberg uncertainty principle starts to wreck havoc on the equations of quantum physics and many quantum gravity theorists have doubts about whether a description of space-time as a continuous manifold (as it is modeled in both the Standard Model and General Relativity) is an accurate description of the universe a such high Planck scale energies and at the tiny distances of the Planck legth.

A core open question in particle physics is whether there are any new physics in the "desert" between the 1 TeV scale phenomena that are experimentally bound and the GUT scale. Wikipedia explains the concept:

In particle physics, the desert refers to a theorized gap in energy scales between the TeV scale and the GUT scale in which no new physics appears. The idea of the desert was motivated by the observation of approximate, order of magnitude, gauge coupling unification at the GUT scale.

Is There An Oasis In The Desert?

Most active research in theoretical physics that is open to the possibility of beyond the Standard Model physics, proposes new physics that can be observed at the low end of the desert, a threshold that continually rises in energy scale as new experiments are conducted without finding new physics. Most supersymmetry theories (and most other GUT theories and many quantum gravity theories) predict that new physics (often subtle) will be discernable in the desert. For example,"[i]f neutrino masses are due to a seesaw mechanism, the seesaw scale should lie within the desert. . . . An alternative to a desert is a series of new physical theories unfolding with every few orders of magnitude increase in energy scale." Supersymmetry proponents hope to identify new supersymmetric particles, the lightest stable one of which could also explain dark matter phenomena seen by astronomers, typically visible at interaction scales of 1 TeV to 20 TeV or so, and having masses on the order of 100 GeV or more (i.e. close in mass to the Higg boson or heavier).

The less skeptical view holds open the possibility that new physics are "just around the corner" and will be discovered, if not during our own lifetimes, during those of our children or grandchildren or great-grandchildren if only our society is committed enough to finding it.

The conservative view is that there are probably no new physics in the desert, and that energy scales we have any serious hope of probing experimentally in the next few decades, or even centuries, are too tiny relative to the GUT scale to show any experimental indication of GUT scale physics. In other words, we are unlikely to discover beyond the Standard Model physics in any experiments that we can conduct in even the dimly foreseeable future.

How Huge Are GUT Scale and Planck Scale energies?

The interactions that are being probed at the Large Hadron Collider involve energy levels that have not been important in the cosmology of the universe after the first microsecond of its existence. We are fairly comfortable that, with the exception of dark matter, pretty much everything that has happened in the universe since then can be explained with the plain vanilla Standard Model of Particle Physics and plain vanilla General Relativity.

(So called "dark energy" isn't really a mystery as adding a single constant into the equations of General Relativity, as Einstein realized might be necessary a century ago, fully explains the observed effects of this phenomena. There are some loose ends in the area of neutrino physics that we haven't yet figured out, but we have good reason to believe that we may be able to figure out those issues within a few decades by simply filling in some only vaguely known values for Standard Model constants and figuring out at what rate (if any) neutrinoless double beta decay occurs.)

Put another way, pretty much all of the expansion of the universe after the first nanosecond (i.e. 10^-9 seconds) after the Big Bang has taken place at energy levels where the Standard Model and General Relativity are valid, and has expanded in size at the speed of light in the roughly 13.7 billion years since then. But, we aren't terribly sure precisely what dimensions the universe had during the first nanosecond of the universe, except that it was 13.7 billion light years across smaller than it is now. One estimate is that the universe was about one foot (10 cm) across at the end of the inflation period that started at around 10^-32 seconds after the Big Bang and might have been as much as seven feet across at the end of the first nanosecond.

(Purists will note that I'm cheating somewhat here, as General Relativity doesn't assign absolute times and distances to universe scale phenomena since these are observe dependent quantities even though there is a consistent way to reconcile the observations of all observers.)

It may require new physics beyond the Standard Model and General Relativity to explain the cosmology of the universe in this first nanosecond of its existence and this is what physicists are looking for now.

Reproducing the energies last routinely found in the universe in its first nanosecond, even if only fleetingly and in tiny volumes of space, is a challenge even for high eergy physicists that is to some extent a fundamental one, since the Big Bang cannot presumably, be reproduced (and we probably wouldn't want to do that even if we could). Squishing the universe (or even a tiny part of it with equivalent matter-energy density) into a package smaller than a compact car is unthinkable as an engineering proposition even with innovations over the entire lifetime of our species.

It isn't at all clear that physics involving interactions at scales where the Standard Model ceases to be an accurate effective low energy approximation of the true laws of the universe (or quantum gravity theories) would have any engineering applications, and even their cosmology implications would apply only to the first nanosecond of the universe's existence. The higher the energy scale beyond 1 TeV at which we fail to find new physics, the more true this conclusion becomes.

Yet More Evidence For Dim Matter

Once again, evidence that some of matter which had been assumed to be "dark matter" not composed of ordinary atoms turns out to be relatively ordinary matter that is simply difficult to observe.  Previous studies have also identified dim ellipical galaxies, gases between galaxies in galactic clusters, and ultrafast objects emitted from black holes at the center of galaxies (UFOs aka "black hole barf"), as important contributors to the total amount of matter in the universe. 

Estimates of the total amount of dark matter in the universe start with estimates of the total amount of matter in the universe via methods like relativistic lensing and then subtract out known sources of ordinary matter from observed or easily inferred sources.  But, the ratios of dark matter to all matter in the universe commonly quoted in scientific journalism directed at the general public does not reflect these multiple new discoveries.  Adjusted for these new discoveries dark matter accounts for only about half of all observed matter.

Equally notably, the latest research shows that the vicinity of galactic clusters is highly atypical of the regions on the fringes of ordinary galaxies, having far more "dim matter" than ordinary galaxies.  Theories like MOND, which estimates of the nature of the effects usually attributed to dark matter based on empirical correlations observed between rotation curves and luminous matter distributions are usually remarkably accurate even with just a single parameter to be fit to the data and do so without requiring the existence of some class of fundamental particle that has been largely ruled out by Earth bound experiments.

In contrast, all existing dark matter theories can only fit the data from ordinary galaxies with multiple parameters and require some, as yet undiscovered, new kind of fundamental particle that is not simply an ordinary atom.  Dark matter theories also have a far weaker track record when it comes to making predictions about not yet observed types of galaxies.

But, these modified gravity theories greatly underestimate the observed effects in galactic clusters.  The large amounts of "dim matter" in galactic clusters may help to explain this discrepency.  For example, even more sophisticated version of MOND simply cannot be fit to the Bullet Cluster collision that has been observed. 

If galactic clusters have large quantities of dim matter that are absent in the vicinity of ordinary galaxies, in addition to ordinary MOND effects (whether its mechanism is true dark matter, or some predictable distribution pattern of dim matter, or from a modified gravity law), the case for a MOND Plus theory to describe galactic clusters the cures the deficiencies of MOND theories in the domains where they fail, sounds plausible.

The Problem and A Possible Solution

Astronomers disagree about why they see more light in the universe than should be seen; that is, why the infrared light they observe exceeds the amount of light emitted from known galaxies.

When looking at the cosmos, astronomers have seen what are neither stars nor galaxies nor a uniform dark sky but mysterious, sandpaper-like smatterings of light, what UCLA professor of physics and astronomy Edward L. (Ned) Wright refers to as "fluctuations".

From here.

The data appear to rule out the possibility that the fluctuations in the infrared background are from very distant unknown galaxies and also rule out the possibility that the fluctuations "have been traveling to us from faint galaxies for only 4 or 5 billion years[.]" 

So what could be going on?  According to Wright:

"Galaxies exist in dark matter halos that are much bigger than the galaxies; when galaxies form and merge together, the dark matter halo gets larger and the stars and gas sink to the middle of the the halo. . . .What we're saying is one star in a thousand does not do that and instead gets distributed like dark matter. You can't see the dark matter very well, but we are proposing that it actually has a few stars in it — only one-tenth of 1 percent of the number of stars in the bright part of the galaxy. One star in a thousand gets stripped out of the visible galaxy and gets distributed like the dark matter. . . . The dark matter halo is not totally dark. A tiny fraction, one-tenth of a percent, of the stars in the central galaxy has been spread out into the halo, and this can produce the fluctuations that we see."

In large clusters of galaxies, astronomers have found much higher percentages of intra-halo light, as large as 20 percent, they contend. 

In addition to having hig percentage of stars that are not a part of particular galaxies, galactic clusters also greatly elevated levels of interstellar gas and could also harbor large quantities of neutrinos.  Leptogenesis theories suggest that there aren't nearly enough neutrinos in the universe to account for all dark matter, but there are more than enough "missing neutrinos" in the universe to account for excessive amounts of non-baryonic matter in galactic clusters.

 

Evidence Mounts For Out Of Africa 100-130 KYA

The Nubian Complex Culture Source In Africa For The First Wave Of Modern Humans To Leave Africa For Inland Arabia Has Been Identified And Accurately Dated Based Upon Archaelogical Evidence From Many Sites In Both Places.

A new published academic paper adds to the increasingly overwhelming evidence which has been published only in the last several years, that modern humans who were part of a Sudanese archaeological culture, called the Nubian Complex, migrated out of Africa to Arabia (for example, into what is now Southern Oman, into Central and Eastern Yemen, and into Central Arabia) sometime in the time frame of 100,000 to 130,000 years ago. 

The Nubian Complex people became a long standing Arabian culture that continued to have a presence in inland Arabia at least until the Middle Paleolithic to Upper Paleolithic transition around 40,000 to 60,000 years ago.  It is quite possible that people regularly moved between Arabia and African during the Middle Stone Age more or less continuously from the time that they first arrived until the Upper Paleolithic transition.

It appears likely that members of the Nubian Complex culture engaged in culturally influential back migrations to Africa during the Middle Stone Age and that members of the Nubian Complex culture made culturally influential migrations to the Levant from interior Arabia as well. 

Arabian Nubian Complex People Are The Likely Source Of The Lithic Tool Innovations That Mark The Middle Stone Age To Upper Paleolithic Transition.

It appears likely, indeed, that the Arabian branch of the Nubian Complex culture may have been the innovators who were the source of the lithic tool transition that appears in modern humans at the dawn of the Upper Paleolithic era.  Their tools in the late Middle Stone Age and early Upper Paleolithic look like clear antecedents to Upper Paleolithic lithic tools in the Levant and Egypt at the dawn of the Upper Paleolithic era, while the Nubian Complex lithic tools of Sudan at that point do not appear to be nearly so closely related.

The Numbian Complex People Were Not The Only Population Of Modern Humans In Arabia During The Middle Stone Age.

By the time that the Upper Paleolithic transition took place, around 40,000 to 60,000 years ago, there were other communities of modern humans in Arabia who had different lithic cultures from this culture. 

The Nubian Complex people of Arabia were probably not very closely related to them (although at the time depths involved, there would have been plenty of time for different branches of the original migrant population to grow quite distinct from each other over time). The origin of the other cultures is not known and may have origins in one or more Africa to Arabia migrations fairly close in time to the Africa to Arabia migration of people belonging to the Nubian Complex culture.

There Are Multiple Scenarios By Which The Eurasian Baseline Of Neanderthal Admixture Could Have Arisen And Become Somewhat Differentiated Between East Eurasians and West Eurasians.

Not later than the Upper Paleolithic transition, and possibly much earlier (perhaps 100,000 to 75,000 years ago), all or almost all Eurasian modern human populations had probably acquired some baseline level in Neanderthal admixture, either as (1) a single common founding population that split into Western Eurasian and Eastern Eurasian founding populations (and perhaps other founding populations that later when extinct) before the Neanderthal genes that had introgressed into the founding population had time to fully homogenize, or (2) a single common founding population that experienced additional and comparable amounts of admixture separately after splitting into a West Eurasian and East Eurasian founding population, or (3) in completely separate but similar parallel admixture events after splitting into West Eurasian and East Eurasian populations with reasonably closely related populations of Neanderthals.

Still, all of these scenarios fit the genetic data best if the split of the Middle Stone Age modern human population of Southwest Asia into proto-West Eurasians and proto-East Eurasians happened prior to or not long after a period of Neanderthal admixture in Southwest Asia or West Asia.

We Have Some Data To Provide A Framwork For Our Understanding Of The Out of Arabia To Asia Migration(s), But Many Details Are Still Not Known.

It increasingly appears that the migration of modern humans from Arabia to the rest of Eurasia came many thousands of years later, although there is fairly clear evidence that some population of modern humans (not necessary a group with ancestors among the Nubian Complex people) had migrated to Southern India no later than 75,000 years ago, and probably considerably earlier although just how much earlier is hard to tell.  Thus, there may have been a delay of as much as 55,000 years between the Out of Africa and the Out of Arabia migration, although the new more accurate dating of older Levantine and Arabian traces of modern humans and new and older finds of traces of modern humans from India could instead narrow the separation between the Out of Africa migration and the Out of Arabia migration to as little as a few thousand years.

It isn't at all clear that the first Out of Arabia to Asia wave that was present in Southern India at the time of the Toba erruption about 75,000 years ago are descendants of the Nubian Complex people. 

We have only relics that are clearly modern human in origin, not human remains, to rely upon this far back in time in Southern India.  The Arabian archaelogical record is also far richer in relics than in human remains although there are some modern human remains at some Arabian Nubian Complex archaeological sites.  The lithic tools in South India are not quite so strikingly similar to the Arabian ones as the Arabian ones are to lithic tools at the African Nubian Complex sites, or at the Levantine and Egyptian sites derived from Arabian Nubian Complex innovations arond the time of the Upper Paleolithic transition. 

Since it is likely that there were multiple modern human populations in Arabia at the approximately the same time that the Nubian Complex people were there during the Middle Stone Age, and since the modern human lithic tools at the earliest Southern Indian sites don't show a particularly clear continuity with Nubian Complex lithic tools, another of the modern human groups in Arabia at the time could have been ancestral to the first wave of modern humans in Southern India.

We know that sometime around 45,000 to 50,000 years ago, presumably via a route that made the connection from Africa to Southeast Asia that passed through India in some way or another, that modern humans arrived in Papua New Guinea and Australia (which were a single land mass at the time) having by then acquired the Neanderthal admixture shared by all Eurasians (and in particular, the East Eurasian subset of that admixture) and the Denisovan admixture which are largely restricted to Aboriginal Australians, Papuans and other populations genetically related to those populations. 

There are traces of modern humans in the Southeast Asian highlands that are no older than 64,000 years old and no younger than 50,000 years ago, probably close to the older date than the younger one.  Modern humans appear to have arrived in Southeast Asia en route to Australia although, of course, they didn't know where they where going at the time) sometime in a twenty-five thousand year time frame bounded by the Toba erruption on one side and the Upper Paleolithic revolution on the other.

The case that hominin remains from East Asia, which have claimed dates of around 100,000 years ago, are really modern humans rather than archaic hominins who may have been experiencing some convergent evolution towards some of the same traits which modern humans evolved, and are really accurately dated, is tenuous at best.  New evidence, however, could strengthen that claim and greatly complicate the emerging narrative of modern human expansion into Eurasia.

Out of West Asia To Europe: Were Cro-Magnons Descendants Of Nubian Complex People?

We also know that sometime around 45,000 to 43,000 years ago, modern human Cro-Magnons who already had West Eurasian genetic affinities distinct from East Eurasian populations arrived in a Europe that was populated by Neanderthals.  It isn't clear what population genetic affinity these Cro-Magnons or later waves of modern human migrants to Europe had to the Nubian Complex people.  But, given that the Nubian Complex people are likely to have been a source of Upper Paleolithic lithic tool technologies, at the very least, the Nubian Complex people were an important cultural inflence on the Cro-Magnons, and it wouldn't be at all surprising given the trend of recent ancient DNA and archaeological finds to reflect "Pots and People" rather than "Pots Not People" migrations, if the Nubian Complex people were key contributors to the gene pool of the Cro-Magnons.

While hardly definitive, what we know so far seems to identify the descendants of the Arabian Nubian Complex people a bit more closely with modern West Eurasians than with modern East Eurasians, who could be more closely related to one or more of the other Middle Stone Age modern human populations of Arabia that were in Arabia at the same time that the Nubian Complex people were there.

The Cro-Magnons very likely became more Neanderthal admixed than the Eurasian baseline level of Neanderthal admixture than they had been when they arrived over the course of the many thousands of years  that they co-existed with Neanderthals between their arrival in Europe and the extinction of the last Neanderthals arond 29,000 years ago. 

But, this pre-Last Glacial Maximum population of European hunter-gatherers that co-existed with Neanderthal was so diluted in subsequent waves of migration to Europe by modern humans.  The later waves of migrants to Europe lacked Neanderthal admixture in excess of the Eurasian baseline level.  So the Neanderthal admiture excess attributable to admixture in Europe's early Cro-Magnons is almost impossible to discern statistically in contemporary European populations.

How can we be confident that the Cro-Magnons did have elevated Neanderthal admixture then? 

Because people with significant amounts of ancestry from European hunter-gatherers were living in Europe as late as Otzi the Iceman who died 5,300 years ago and was preserved as a mummy in the ice on mountains between what are now Austria and Italy did have elevated levels of Neanderthal admixture.

It Isn't Entirely Clear What Relationship The Arabian Nubian Complex People Have To Linguistically Afro-Asiatic Africans Today.  They May Have Been A First Wave Of Back Migrating Eurasian Genetic Contributors To This Population.

These data points would be consistent with a hypothesis that many of the older non-replicating Y-DNA and mitochondrial DNA haplogroups that now coincide rather strongly with modern Afro-Asiatic populations could derive from a back migration of Nubian Complex people from Arabia into Africa in which the technological edge that allowed them to expand more effectively into territory previously inhabited by other peoples may have been the tool kit of the lithic tools that would become signatures of the Upper Paleolithic transition.  Of course, none of these data points can rule out a much later Neolithic or Epipaleolithic back migration as the main source of Asian to African back migrated haplogroups either.

Without ancient DNA we can't know for sure that this Nubian Complex population was ancestral to modern Eurasians, or to modern North and East Africans, at all.  There have been multiple extremely arid periods since the Nubian Complex people left Africa and came to Arabia when Arabia has been entirely or almost entirely depopulated.

No known language family today has a time depth of much more than 8,000 to 10,000 years from a most recent common proto-language, and some of the well defined subfamilies of the Afro-Asiatic language family are considerably young.  So, I am not willing to conclude that the direct ancestor of the Afro-Asiatic language family itself was spoken 40,000 or more years ago.  But, a migration into the modern Afro-Asiatic language region at that time may have had an important and formative impact on the population genetics of that region.  The people of that region may even have had enduring culture ties with each other relative to other contemporaneous modern humans for most of time period since then. 

Populations with powerful new technologies and cultural innovations (such as Neolithic era or even Copper Age peoples) could easily have brought about a language shift of this entire, far flung population to their language, however.  And, a Neolithic or Copper Age population could have brought about language shift with only a modest population genetic impact at some later date.

Conclusion

There are still many questions to be resolved about human pre-history in the Paleolithic era.  But, our understanding of modern human range expansion outside Africa during the Paleolithic era is much greater than it was even a decade ago.

Our ability to link the first Out of Africa wave of modern human migration to a particular archaeological culture has many practical benefits for further research.  For example, it provides an additional reasonably certain calibration point for mutation rate based dating of the point in time at which the defining mutations of genetic haplogroups arose.  It also provides an independent and direct means of estimating critical demographic parameters like the effective population size of the proto-Eurasian population that together with the calibration point and our knowledge of modern human mutation rates from other sources can be used to more accurately determine the parameters to use when modeling the population genetics of Eurasian prehistory in variety of contexts.  These details can reduce the size of the error bars associated with all efforts to assign absolute dates to ancestry informative genetic mutations.

Obscure Genius

Today, I am going to pick on Vladimir Voevodsky, who is certainly an interesting enough fellow in his own right someone who is trained in mathematics (which is his disciplinary field as a professor) with strong interests in problems relevant to fundamental physics and to population genetics. As I note below, if we ever run into each other, I owe him a few drinks for subjecting him to a somewhat down beat assessment of the individual life accomplishments of this extraordinary man in my post today. But, today, I am more interested in talking about the personal niche he is in, which is shared by a great many others, than is personal accomplishment per se.

Voevodsky in a middle aged guy (he is a few years older than I am, but our years studying at institutions of higher education in the United States overlapped) who did his undergraduate work in Moscow, left to the U.S. to do graduate work at Harvard around the time that the Soviet Union fell, is a math professor at Princeton, and won a Field medal, which is basically the Nobel Prize of mathematics, in 2002. He is by any reasonable account a genius.

Voevodsky, like some many other geniuses, however, is an obscure genius. According to a colleague writing a short biography of him, "he defined and developed motivic cohomology and the A1-homotopy theory of algebraic varieties; he proved the Milnor conjectures on the K-theory of fields."

Don't be ashamed that you have no idea what that means.  I struggle to understand it, and I skipped to years of undergraduate math in college and instead spent all three of my years in college taking 300 and 400 level math courses.  Unless you have taken abstract algebra, topology, and real and complex analysis, which are typically offered as 400 level undergraduate course to mathematics majors or 500 level courses for graduate students, you really have not a prayer of meaningfully understanding even a non-specialist oriented description of what is work involves. Few people who aren't professionals in the relevant field know his name (those who are professional in the relevant field hold him in very high esteem), and not even sophomore or junior math majors at esteemed colleges and universities (other than Princeton, of course) have heard of him.

Voevodsky's name isn't familiar to politicians and journalists (except a handful of very sharp science journalists with good memories), won't earn him VIP seats at a ballgame or a nice restaurant outside his home town, and probably gets spelled wrong on his junk mail. A decade from now, more people will remember the name of Missy Franklin, a Denver high school student who won a gold medal for swimming in this year's Olympics, than remember today his shining moment in the sun during the year when he was recognized that year as one of the world's premier mathematicians.

None of this is to put him down. If I met him, I'd know his name and I'd certainly look forward to sharing a beer and talking shop in some dark pub (being Russian, he might be a vodka man, and that would be cool too), my treat.

My point is that our very civilization as an advanced complex technological society rests of the collective achievements of thousands of people like him - the creme de la creme of the upper middle class in who excel in a whole panoply of sometimes obscure professional endeavors. They generally live comfortable upper middle class lifestyles, but are usually neither famous nor genuinely rich on the scale of the thousands of people who have net worths of a hundred million dollars or more. Economically, they live the lives of other successful middle managers in big business and professionals who aren't top level employees of law firms and big businesses.

In truth, we could survive without any one of them and wouldn't know the difference. Lots of people wonder what more could have been discovered is Shakespeare had written another play, if Percy Shelly had written another poem, if Feynman had survived another decade, if Mozart had finished another symphony, or if Fermat had been able to work full time on mathematics rather than merely doing it as a hobby. But, were he to be hit by a bus today, nobody but his family, his graduate students, and his fellow department members at Princeton will dwell on what further conjectures in group theory or topology Voevodsky might of proved or proposed beyond his already formidable accomplishments in another decade once he completes his career. Collectively, the impact of obscure geniuses like Voevodsky in a whole range of professions, is enormous. The group effort that is the produce of their endeavors keeps science and the organization of our society moving ever forward.

This situation certainly isn't particular to mathematics. There are six thousand scientists working at the Large Hadron Collider for instance, many of them doing truly intellectually demanding, cutting edge physics every day, on deadline, as a matter of course and these near geniuses have to have enough social skills to be team players as well. Probably at least one or two hundred of them are geniuses who have made contributions to the enterprise that really no one but a genius could manage and are highly esteemed in their field by their colleagues who can understand their accomplishments and talents. But, fewer than a dozen of them will ever be any more famous than Mr. Voevodsky, even to new generations of students within their field.

Mr. Voevodsky is also notably, not just as an individual Russian mathematician, but also as a member of a numerically small mass migration of the creme of the intellectual elite for the former Soviet Union and Eastern Europe that experienced economic collapse before the recovery began again to the West and, in particular, in large numbers to the United States. The world hadn't seen anything like it since the years immediately before and after World War II. This mass migration of this key elite population has had a rise and fall of great powers level of significance in geopolitics and science that several studies of elite performances in the sciences have documented, although it is little known. It had breathed new blood and new ideas into American science, technology and academics, exposing technical scientific knowledge and ideas that had been isolated in the Eastern block and was little known outside it to a much wider audience where the new ideas have cross-pollinated with Western ones.

Maybe one somewhat obscure Field medal class mathematician like Voevodsky will accomplish in his professional life is a tenth or a twentieth of what a mathematical legend known to all math students at the high school level and beyond, like Euler, did. But, there are at least ten or twenty mathematicians of Voevodsky's caliber, probably more, alive today and they are all working hard at their crafts and standing of the shoulders of the giants who came before them. They also have more colleagues who can understand their work and help prod them on to greater achievements with their own insights. And, very few of them are likely to die young and have their potential prematurely cut short, unlike so many of the famous geniuses of earlier times.

Physics Blog Notes One Of My Comments

Over at Tommaso Dorigo's Quantum Diaries Survivor blog, an analogy I made in a comment, that one could use to describe the issue of naturalness in the cancellation of higher order loop corrections in quantum mechanics to a layman, has been made the subject of one of the blog's main posts for today.

Hurray!

The Limits Of Scientific Confidentiality

All in all, I’m fairly happy with my decisions about what to write and what not to write on the blog about not-quite-public results about the Higgs. There’s been a certain amount of criticism about the terrible violations of confidentiality involved, but I can’t help pointing out that the things I was writing about were at the time known to the majority of the HEP community: the 6000 physicists on ATLAS and CMS. Carroll has this to to report about the confidentiality question:

I asked one physicist whether the results that ATLAS was getting were generally known within CMS, and vice versa. “Are you kidding?” I was told with a laugh. “Half of ATLAS is sleeping with half of CMS. Of course they know!”
 

From Not Even Wrong.

Lawyers have long been aware of these kinds of issues and have developed ethical standards for addressing them in their own profession, the official commentary to the analogous ethical rule:

When lawyers representing different clients in the same matter or in substantially related matters are closely related by blood or marriage or when there is a cohabiting relationship between the lawyers, there may be a significant risk that client confidences will  be revealed and that the lawyer's family or cohabiting relationship will interfere with both loyalty and independent professional judgment.  As a result, each client is entitled to know of the existence and implications of the relationship between the lawyers before the lawyer agrees to undertake the representation.  thus, a lawyer related to another lawyer, e.g., as parent, child, sibling or spouse (or in a cohabiting relationship with anothe lawyer,) ordinarily may not represent a client in a matter where that lawyer is representing another party, unless each client gives informed consent.  the disqualification arising from a close family relationship or a cohabiting relationship is personal and ordinarily is not imputed to members of firms with whom the lawyers are associated. . . . A lawyer is prohibited from engaging in sexual relationships with a client unless the sexual relationship predates the formation of the client-lawyer relationship.
 

Colorado Rule of Professional Conduct 1.7, Official Comment Paragraphs 10 and 11 (this is identical to the official commentary to the American Bar Assocation's Model Rules of Professional Conduct.  Almost every U.S. jurisdiction uses the Model Rules, or the predecessor set of Model ethics guidelines for attorneys promulgated by the ABA, as the starting point for their own rules governing ethics for lawyers).

Other parts of the official commentary to the ethical rules for lawyers explains that for lawyers representing organizations, relationships with certain individuals in the organizations have the same effect as if that individual, rather than the organization that the individual is affiliated with, were the client.

John Hawks In Boulder On Friday

John Hawks will be giving a talk in Boulder, Colorado at 4:00 p.m. this Friday on the Neanderthal genome.  Health and workload permitting, I plan to go and then to blog on the talk here.