Tuesday, January 16, 2018

Two Egyptian Mummies Sharing A 12th Dynasty Tomb Were Half Brothers

Despite previous evidence to the contrary, two mummies from almost four thousand years ago have been determined to be half-brothers based upon ancient DNA analysis. Science News provides an educated layman's level explanation:
The tomb dates to ancient Egypt’s 12th Dynasty, between 1985 B.C. and 1773 B.C. 
Coffin inscriptions mention a female, Khnum-Aa, as the mother of both men. And both mummies are described as sons of an unnamed local governor. It has always been unclear if those inscriptions refer to the same man, but discoverers decided the mummies were full brothers, because the two were buried next to each other and had the same mother. 
Over time, differences discovered in the men’s skull shapes and other skeletal features raised suspicions that the Two Brothers were not biologically related at all. And some researchers argued that the inscriptions indicating the men had the same mother were misleading. 
Adding to those doubts, a 2014 paper reported differences between the two mummies’ mitochondrial DNA, suggesting one or both had no biological link to Khnum-Aa. Mitochondrial DNA typically gets inherited from the mother.
But that study extracted ancient DNA from liver and intestinal samples using a method susceptible to contamination with modern human and bacterial DNA, Drosou’s team argues. In the new work, researchers isolated and assembled short pieces of mitochondrial and Y-chromosome DNA from both mummies’ teeth using the latest methods. The Y chromosome determines male sex and gets passed from father to son. This approach minimizes potential contamination from modern sources.
This discovery contributes to a mosaic of other evidence suggesting that succession to leadership positions in the early Egyptian kingdom may have been from mother to child, rather than from father to son. 
We resolve a longstanding question regarding the kinship of two high-status Egyptians from the 12th Dynasty, Nakht-Ankh and Khnum-Nakht, whose mummies were discovered in 1907 by Egyptian workmen directed by Flinders Petrie and Ernest Mackay. Although their coffin inscriptions indicate that Nakht-Ankh and Khnum-Nakht were brothers, when the mummies were unwrapped in 1908 the skeletal morphologies were found to be quite different, suggesting an absence of family relationship. We extracted ancient DNA from the teeth of the two mummies and, following hybridization capture of the mitochondrial and Y chromosome fractions, sequenced the DNA by a next generation method. Analysis of single nucleotide polymorphisms showed that both Nakht-Ankh and Khnum-Nakht belonged to mitochondrial haplotype M1a1, suggesting a maternal relationship. The Y chromosome sequences were less complete but showed variations between the two mummies, indicating that Nakht-Ankh and Khnum-Nakht had different fathers. Our study emphasizes the importance of kinship in ancient Egypt, and represents the first successful typing of both mitochondrial and Y chromosomal DNA in Egyptian mummies.
K. Drosou, C. Price and T. Brown. The kinship of two 12th Dynasty mummies revealed by ancient DNA sequencing. Journal of Archaeological Science: Reports. Vol. 17, February 2018, p. 793. doi:10.1016/j.jasrep.2017.12.025.

The new result contradicts a previously analysis from 2014 done using methods more prone to contamination. C. Matheson et al. Molecular confirmation of Schistosoma and family relationship in two ancient Egyptian mummies. In H. Gill-Frerking et al., editors, Yearbook of Mummy Studies Volume 2, p. 39.

Monday, January 15, 2018

Ethiopia Was A Trade Hub In The Classical Era

In ancient times, long-distance trade was the umbilical cord linking Ethiopia and the outside world. Ethiopian merchants spread their wares far and wide, including incense, ivory, gold, and even live animals such as baboons. Its closest trading partners lay just across the Red Sea in southern Arabia, but Ethiopian traders also reached markets in far-away Egypt, India, and the Mediterranean. So numerous were the Ethiopian merchants of Alexandria, for example, that a fourth-century Roman law barred them from tarrying in the city for more than a year. These commercial contacts encouraged cultural exchange, such that Ethiopia’s art, architecture, and literature were constantly shaped by the practices of its distant neighbors.
From a review of a book about the Garima Gospels, some of the oldest known Biblical manuscripts.

Thursday, January 11, 2018

Some Observations On West Eurasian Historical Linguistics

This post is a collection of linguistic history data points, without necessarily reaching a full conclusion.

From Edward Pegler at Armchair History (November 12, 2017):
2: What about the Anatolian languages? 
The Mathieson et al. (in review as of 2017) paper currently circulating in various forms, refutes one particular argument of David Anthony 2007 and others, which is that there was much migration from the steppe into Anatolia between 4000-2000 BC. This has been further backed up by Lazaridis et al. 2017. 
This means that any migration to the Balkans around 4000 BC is unlikely to have affected Anatolia and, therefore, that Anatolian IE languages are unlikely to have got to Anatolia via the Balkan route. Any potential early PIE languages coming southwest from the Ukraine are therefore likely to have got stuck in the Balkans. We have no evidence for any such language as all well attested IE languages of the Balkans appear to be from the later migrations (Yamnaya or even later). 
Instead, the evidence of an increase in genetic contribution from the Caucasus (or, less likely, Iran) suggests migration from the East into Anatolia during this period. 
What this tells us about Anatolian languages is difficult to say. As Mathieson et al. state, the sampling in Anatolia is not extensive, and maybe they’ve just been unlucky in not sampling the right ancient people in Anatolia. However, there is generally quite a lot of consistency in their samples for different areas, so this seems questionable. 
This leaves two theories for the Anatolian languages. The first is that they are home grown, as Colin Renfrew argued. Realistically, the likelihood of this is low, based on linguistic evidence of language replacement by Anatolian languages (oh how blind I was). The other is that Anatolian languages originated somewhere near or in the Caucasus (or Iran). . . .
Lazaridis I. et al. 2016 Genomic insights into the origin of farming in the ancient Near East, Nature 536, 419-424. 
Very important paper for detailing Anatolia, Armenia and NW Iran genetics. This shows the strange continuity of Armenia during the period under study. 
Lazaridis I. et al. 2017 Genetic origins of the Minoans and Mycenaeans, Nature 548. 214-8. . . . 
Mathieson, I. et al. (in press) The Genomic History of Southeastern Europe, (review copy posted on bioarxiv 9 May 2017, revised 19 September) 
This contains a very good summary of the genetic data for Europe, largely in diagramatic form, within the supplements.
I have long argued based upon archaeological evidence and contemporaneous historical accounts by Akkadian traders, that the Anatolian languages, despite being linguistically very divergent from the other Indo-European language families, actually date from ca. 2000 BCE, a result that Lazaridis (2017) and Mathieson (2017) now affirm with ancient DNA data.

In my view the apparent linguistic antiquity of the Anatolian languages is actually a product of substrate influences which seems stronger than in other Indo-European languages because the substrate was more divergent (and because the proto-Anatolians may have been less dominant and less numerous during the period of Anatolian language formation). There is pretty good linguistic evidence to suggest that the relative contributions of language contact and drift to language change is much more heavily weighted towards language contact than is widely assumed (I'll save the detailed evidence of that for another day.) 

Also, other Indo-European languages had substrate languages which were all much more similar to each other as a result of their common origins in First Farmer languages which themselves have common origins, and if there is a shared change in a group of languages due to parallel interactions with similar substrates, this makes the direction and nature of language change non-random and makes these languages look younger than they really are.

In my view, the Caucasian genetic influence that is observed in the ancient DNA data in Anatolia is attributable to an earlier Bronze Age migration of non-Indo-European Caucasians into Anatolia in the Enolithic/early Bronze Age period prior to the arrival of Anatolian language bearers such as the Hittites, and this genetic shift, instead, reflects the people who brought the Hattic religion and language to Anatolia, supplanting the First Farmers of Anatolia whose descendants spread farming and herding to mainland Europe.
3: What about Armenian? 
The Armenian language is a similar problem. The genetics of Armenia is non-steppe and appears to have been so since at least the 5th millennium BC, being basically a mix of CHG and Anatolians/EEF. Since then genetic change in the area has been gently toward Iran, Anatolia and the Middle East. In fact, unlike northern Europeans, Armenians have not changed that much genetically in the last 6000 years. There is no particular evidence for a major immigration event during this time. 
I should mention the presence of ancient Y-haplogroup R1b1a1 in Armenia in an individual of the 3rd millennium BC, and of R1b1a1a and sub-clades from the 2nd millennium BC and 1st millennium BC. The first is ambiguous and could be due to male intrusion into the area of modern Armenia from the west or the steppe (more likely the steppe). The others are clearly due to steppe intrusion. What numbers of male individuals are implicated and on how many occasions is difficult to say, but it could not have been large. 
Whilst the language of Armenian is not recorded in ancient texts (it’s earliest record is the 5th century AD) it appears to have been knocking around in its present area since at least the 1st millennium BC based on the evidence of loanwords into neighbouring Iron Age languages. Coupled with the genetic info, this means that either the precursors of Armenian have been in NE Anatolia since the 5th millennium BC or a small elite managed to change the language of this region before the 1st millennium BC, something which, as with the Anatolian languages, is quite hard to do. 
In combination this makes a steppe origin for the Armenian language, arriving perhaps in 3rd millennium BC, possible but not very easy. . . .
The mysteries of the Armenian language, in my view, also reflect an underestimation of the importance of language contact.

The Armenians are at a complex linguistic boundary. To the east, Indo-Iranian languages and for a while, Indo-Aryan languages were spoken. To the west, Anatolian languages, especially Hittite, was spoken, and then later, the entire region was subsumed in Greek speakers. To the north, Indo-European languages of the steppe were spoken. As a result of these successive influences from different families of Indo-European languages, litmus tests like the satem-centum isogloss fail to capture the complex multi-layered process of language formation in Armenian, which may also have been influenced to some extent by neighboring non-Indo-European languages.

Also, it is worth noting that the apparent genetic continuity of Armenia, upon which this blogger relies, depends upon the findings of a paper whose poor methodology was later debunked. In fact, we know very little about whether or not Armenia displays continuity in genetic population, notwithstanding one overstated claim base upon a poor analysis of ancient DNA.
[K]nowing what I know now about the fact that Slavic peoples made their way into the Balkans from the North and had a significant demic component (unlike many other migration period "barbarians"), it isn't implausible that at least some of the Y-DNA R1a in the Balkan region today arrived as late as the Iron Age from Slavic migration (which would have predominantly Y-DNA R1a relative to Y-DNA R1b), and that the ratio of R1b to R1a in the Balkan region was higher in the Bronze Age than it is today. And, the R1b blending proportions with R1a in the Balkans, unlike in many other parts of Europe, is not a good fit to historical boundaries between the Bell Beaker cultural area and the Corded Ware cultural area that succinctly describes the relative proportion of these Y-DNA types in most of Europe. So there is a window in time in the Bronze Age during which R1b could plausibly have been dominant in a population that migrated through Western Hungary on to Western Europe.
From a June 30, 2015 post at this blog.

This is also a fairly important observation, which is also supported by many of the "Serbian-Irish" observations at the Old European Culture blog. While the big Bell Beaker paper, i.e. Olalde, I. et al. (in press) The Beaker Phenomenon and the Genomic Transformation of Northwest Europe, (review copy posted on bioarxiv 9 May 2017), notes that there is discontinuity in ancient DNA between Iberian Bell Beaker people and those of the rest of Europe, the hypothesis of this June 30, 2015 post could go a long way towards offering up a narrative that can explain the demic shift outside of Iberia that coincides closely in time and space with the Bell Beaker culture, which is probably, in my view, derived from the Southern Steppe, Y-DNA R1b Yamnaya people, while the Corded Ware and Slavic people are probably derived from sister populations in the northern part of the European steppe. The R1b people disappear at a historical moment well defined by ancient DNA and Central and Western Europe and to a lesser extent Northern Europe, is probably where they went.

Wednesday, January 10, 2018

A New Review Of Fertile Crescent Neolithic Revolution Genetics

I missed this paper about the genetics of the Neolithic Revolution (i.e. the domestication of plants and animals giving rise for the first time to farmers and herders in addition to hunter-gatherers and people who subsist on fishing) when it came out during Thanksgiving Week (and found it today on Razib's Twitter feed).

I emphasize the big points in the abstract of the paper below, that: (1) Anatolian Neolithic people arose from local hunter-gatherers rather than neighboring populations that were genetically different which also participated in bringing about the Fertile Crescent Neolithic Revolution, and (2) the Aegean Neolithic involved a distinct group of people from the larger mainland European Neolithic.

Both of these findings are largely unsurprising to folks who have read the previous discoveries which this paper summarizes, analyzes and synthesizes.
The Neolithic transition in west Eurasia occurred in two main steps: the gradual development of sedentism and plant cultivation in the Near East and the subsequent spread of Neolithic cultures into the Aegean and across Europe after 7000 cal BCE. Here, we use published ancient genomes to investigate gene flow events in west Eurasia during the Neolithic transition. 
We confirm that the Early Neolithic central Anatolians in the ninth millennium BCE were probably descendants of local hunter–gatherers, rather than immigrants from the Levant or Iran. We further study the emergence of post-7000 cal BCE north Aegean Neolithic communities. Although Aegean farmers have frequently been assumed to be colonists originating from either central Anatolia or from the Levant, our findings raise alternative possibilities: north Aegean Neolithic populations may have been the product of multiple westward migrations, including south Anatolian emigrants, or they may have been descendants of local Aegean Mesolithic groups who adopted farming. These scenarios are consistent with the diversity of material cultures among Aegean Neolithic communities and the inheritance of local forager know-how. The demographic and cultural dynamics behind the earliest spread of Neolithic culture in the Aegean could therefore be distinct from the subsequent Neolithization of mainland Europe.
Gülşah Merve Kılınç, et al. "Archaeogenomic analysis of the first steps of Neolithization in Anatolia and the Aegean" Proceedings of the Royal Society B (November 22, 2017) (open access).

Etruscans in early Iron Age Sardinia

The Etruscans were the last people (or nearly so), other than the Basque, whose language is a language isolate; the Finns, the Saami, the Hungarians and a few Russian minorities who speak Uralic languages; and relatively recently arrived Jews and Muslims (speaking Semitic languages); to speak a non-Indo-European language in Europe.

The Etruscan language was historically attested in Roman historical documentation from 700 BCE into the common era (50 CE), but the language was extinct and the culture largely lost before the Roman Empire fell. Also, while this language is attested in writing, we haven't deciphered what it means (and don't know where it fits in a linguistic family tree). Indeed, but for the historical records and written examples of the Etruscan language, archaeologists would have assumed that they were Indo-European Italic language speakers with a slightly different religious cult and artistic sensibility than their neighbors in Iron Age Northern Italy.

Essentially all Etruscan archaeology derives from Tuscany and the immediate vicinity in Northern Italy, with a smattering of historical attestations from ex-patriot Etruscan communities in major Roman empire cities like the capitol in Rome.

But, now, Etruscan archaeological evidence has surfaced in Sardinia:
An Etruscan settlement that dates back to the 9th century BC has been found on the Sardinian coasts near Olbia. The presence emerged during a review of the findings of recent years by the archaeological superintendency for the Sassari and Nuoro provinces.
The Monte Prama statues in Sardinia also date back to those times. ''The exchanges between 'nuraghic' Sardinia and the cultural aspect of the first Age of Iron of Ertruria, known as 'villanoviano' are well known and have been studied in depth. 
However, the presence of a community coming from the Etruscan shore that settled in Sardinia and prospered had not previously been found,'' archaeologist Francesco di Gennaro said. ''It is an absolute first and constitutes a leap forward in the reconstruction of relations between the two shores of the Tyrrhenian in protohistory.''
This materially expands our understanding of the range of Etruscan culture, which even linguistic hypotheses suggesting that Etruscan culture once had a larger range usually associate with other non-Indo-European linguistic communities to the Alps inn the north and the Aegean to the east of Tuscany (the Tyrsenian languages), not in the direction of Sardinia to the west, in the direction of Vasconic linguistic communities (although some Tyresian language was thought to have been spoken at one point on part of the island of Corsica immediately to the North). The possible sister language Lemnian in the Aegean was extinct in the 3rd century BCE. The almost certain sister language Rhaetic in the Alps (not to be confused with the modern Romance language of Switzerland of the same name) died out around the 3rd century CE, a couple of centuries after Etruscan was replaced by Latin.

The publicly available information, summed up above, isn't very rich, but this is still a very important data point in piecing together the state of Mediterranean Europe at the dawn of the Iron Age, and also provides a critical link in trying to find connections between the Etruscan archaeological civilization and language and the linguistic and cultural landscape of  Southern Europe in the Bronze Age.

Also, given the fact that there is a fair amount of ancient DNA from Europe before, during and after this era, including some ancient DNA from Sardinia (another new paper showing Phoenician ties in Sardinian ancient DNA also just came out this year) and from the Etruscans (alas limited to mtDNA), and that the modern population genetic of the relevant regions are relatively well studied, it isn't unthinkable that this clue may allow us to make more sense of that genetic data.

The Phoenician and Sardinian ancient DNA paper is as follows (hat tip to Eurogenes) and overlaps the time frame of the Etuscan settlement in Sardinia.
The Phoenicians emerged in the Northern Levant around 1800 BCE and by the 9th century BCE had spread their culture across the Mediterranean Basin, establishing trading posts, and settlements in various European Mediterranean and North African locations. Despite their widespread influence, what is known of the Phoenicians comes from what was written about them by the Greeks and Egyptians. In this study, we investigate the extent of Phoenician integration with the Sardinian communities they settled. We present 14 new ancient mitogenome sequences from pre-Phoenician (~1800 BCE) and Phoenician (~700–400 BCE) samples from Lebanon (n = 4) and Sardinia (n = 10) and compare these with 87 new complete mitogenomes from modern Lebanese and 21 recently published pre-Phoenician ancient mitogenomes from Sardinia to investigate the population dynamics of the Phoenician (Punic) site of Monte Sirai, in southern Sardinia. Our results indicate evidence of continuity of some lineages from pre-Phoenician populations suggesting integration of indigenous Sardinians in the Monte Sirai Phoenician community. We also find evidence of the arrival of new, unique mitochondrial lineages, indicating the movement of women from sites in the Near East or North Africa to Sardinia, but also possibly from non-Mediterranean populations and the likely movement of women from Europe to Phoenician sites in Lebanon. Combined, this evidence suggests female mobility and genetic diversity in Phoenician communities, reflecting the inclusive and multicultural nature of Phoenician society.
Matisoo-Smith E, Gosling AL, Platt D, Kardailsky O, Prost S, Cameron-Christie S, et al. (2018) Ancient mitogenomes of Phoenicians from Sardinia and Lebanon: A story of settlement, integration, and female mobility. PLoS ONE 13(1): e0190169. https://doi.org/10.1371/journal.pone.0190169

Tuesday, January 9, 2018

Slavs Are Genetically All The Same, Siberians Are Each Distinct In Their Own Way

The Slavic people are generally almost identical genetically (except for Russian Starovers who have 5%-10% Central Siberian admixture). This is notable since Slavic expansion happened starting about 1500 years ago, suggesting a replacement scenario for large swaths of territory during the Migration Period in Europe, rather than fixation reach through spouse exchange between genetically diverse populationos over a long period of time.

Siberian populations show Turkic, Uralic and Indo-European contributions in ways that are complex. Some language groups are genetically connected across long distances with some instances of language shift, and some populations are particularly complex mixes of multiple populations. In these cases, the Turkic genetic contribution is the late arrival to the party (although still more recent arrivals for most of their range than the Slavs), coming thousands of years after the Uralic and Indo-European presences in most of this region.
Background: The history of human populations occupying the plains and mountain ridges separating Europe from Asia has been eventful, as these natural obstacles were crossed westward by multiple waves of Turkic and Uralic-speaking migrants as well as eastward by Europeans. Unfortunately, the material records of history of this region are not dense enough to reconstruct details of population history. These considerations stimulate growing interest to obtain a genetic picture of the demographic history of migrations and admixture in Northern Eurasia. 
Results: We genotyped and analyzed 1076 individuals from 30 populations with geographical coverage spanning from Baltic Sea to Baikal Lake. Our dense sampling allowed us to describe in detail the population structure, provide insight into genomic history of numerous European and Asian populations, and significantly increase quantity of genetic data available for modern populations in region of North Eurasia. Our study doubles the amount of genome-wide profiles available for this region. 
We detected unusually high amount of shared identical-by-descent (IBD) genomic segments between several Siberian populations, such as Khanty and Ket, providing evidence of genetic relatedness across vast geographic distances and between speakers of different language families. Additionally, we observed excessive IBD sharing between Khanty and Bashkir, a group of Turkic speakers from Southern Urals region. While adding some weight to the “Finno-Ugric” origin of Bashkir, our studies highlighted that the Bashkir genepool lacks the main “core”, being a multi-layered amalgamation of Turkic, Ugric, Finnish and Indo-European contributions, which points at intricacy of genetic interface between Turkic and Uralic populations. Comparison of the genetic structure of Siberian ethnicities and the geography of the region they inhabit point at existence of the “Great Siberian Vortex” directing genetic exchanges in populations across the Siberian part of Asia. 
Slavic speakers of Eastern Europe are, in general, very similar in their genetic composition. Ukrainians, Belarusians and Russians have almost identical proportions of Caucasus and Northern European components and have virtually no Asian influence. 
We capitalized on wide geographic span of our sampling to address intriguing question about the place of origin of Russian Starovers, an enigmatic Eastern Orthodox Old Believers religious group relocated to Siberia in seventeenth century. A comparative reAdmix analysis, complemented by IBD sharing, placed their roots in the region of the Northern European Plain, occupied by North Russians and Finno-Ugric Komi and Karelian people. Russians from Novosibirsk and Russian Starover exhibit ancestral proportions close to that of European Eastern Slavs, however, they also include between five to 10 % of Central Siberian ancestry, not present at this level in their European counterparts. 
Conclusions: Our project has patched the hole in the genetic map of Eurasia: we demonstrated complexity of genetic structure of Northern Eurasians, existence of East-West and North-South genetic gradients, and assessed different inputs of ancient populations into modern populations.
Triska et al., Between Lake Baikal and the Baltic Sea: genomic history of the gateway to Europe, BMC Genetics, 2017 18(Suppl 1):110, https://doi.org/10.1186/s12863-017-0578-3

Hat tip to Davidski at Polishgenes Blog. A comment from that post is notable:
Slumbery said... 
The modern Bashkirs live where Hungarians lived before moving west and probably this is the place where their Turkic-Uralic "amalgam" formed. (At least the elite of the end 9th century conquerors was such an amalgam.) Among the sampled populations Khanty are the closest to modern Hungarian linguistically. (The actual closest is Southern Mansi, but that population is not sampled here.) So it makes some historical sense that among the sampled Uralic speaking populations Khanty have the most IBD sharing with Bashkirs. 
January 6, 2018 at 8:53 PM

Thursday, January 4, 2018

What Ecological Impact Did A Meteor Strike 800,000 Years Ago In SE Asia Have?

About a million years after Homo Erectus arrives in Southeast Asia and East Asia from Africa, and probably before or at around the same time as, the appearance of a common ancestor of Neanderthals and Denisovans, and maybe even a common ancestor of that clade and modern humans an asteroid slams into Southeast Asia causing immense short term climate effects, although not a mass extinction. There has been no bigger impact on Earth since then. Three mysteries remain.

First, where precisely was the impact crater? 

The event has been known to scientists in the field for many years, but the latest discoveries narrow the search to Southeast Asia, in someplace where erosion and the like would make the impact site less obvious than it would otherwise be.

Second, what ecological impact did it have?

There isn't much in the archaeological or fossil record to indicate that this was associated with a mass extinction event or a major ecological shift, but this record, particular in Southeast Asia, is very thin. 
A kilometer-size asteroid slammed into Earth about 800,000 years ago with so much force that it scattered debris across a 10th of our planet’s surface. Yet its impact crater remains undiscovered. Now, glassy remains believed to have come from the strike suggest the asteroid hit southeast Asia as our close ancestors walked the Earth.

“This impact event is the youngest of this size during human evolution with likely worldwide effects,” says Mario Trieloff, a geochemist at the University of Heidelberg in Germany not involved in the research. Large impacts can disrupt Earth’s climate by spewing dirt and soot high into the atmosphere, where it can block sunlight for months or even years. . . .

They’re puzzled why a crater that’s both presumably large and geologically young—meaning it hasn’t been exposed to much erosion due to rain and wind—hasn’t been found. The crater, if discovered, could also shed light on how the impact affected life nearby. “Our not-too-distant ancestors witnessed this impact,” Cavosie says. “They might have been dragging their knuckles, but an event like the formation of a 50- to 100-kilometer-diameter impact is sure to have gotten their attention.”
Third, is it plausible that this impact created conditions that spurred the evolution of Neanderthals, Denisovans and maybe even modern humans as well, by placing greater demands for intelligence and adaptability on the hominins in existence at the time?

While this particular data point is hardly conclusive and really no more than a conjecture, collectively, the evidence points pretty strongly towards key moments of punctuated change driven by climate and extraterrestrial events in what is known as the Court Jester Hypothesis.

From Science Magazine.
Australasian tektites are enigmatic drops of siliceous impact melt found in an ~8000 × ~13,000 km strewn field over Southeast Asia and Australia, including sites in both the Indian and Pacific oceans. These tektites formed only 790,000 yr ago from an impact crater estimated to be 40–100 km in diameter; yet remarkably, the young and presumably large structure remains undiscovered. 

Here we report new evidence of a rare high-pressure phase in Australasian tektites that further constrains the location of the source crater. The former presence of reidite, a high-pressure polymorph of zircon, was detected in granular zircon grains within Muong Nong–type tektites from Thailand. The zircon grains are surrounded by tektite glass and are composed of micrometer-sized neoblasts that contain inclusions of ZrO2. Each grain consists of neoblasts in three distinct crystallographic orientations as measured by electron backscatter diffraction, where all directions are orthogonal and aligned with one direction from the other two orientations. The systematic orientation relationships among zircon neoblasts are a hallmark of the high-pressure polymorphic transformation to reidite and subsequent reversion to zircon. The preserved microstructures and dissociation of zircon to ZrO2 and SiO2 require a pressure >30 GPa and a temperature >1673°C, which represent the most extreme conditions thus far reported for Australasian Muong Nong–type tektites. The data presented here place further constraints on the distribution of high-pressure phases in Australasian tektites, including coesite and now reidite, to an area centered over Southeast Asia, which appears to be the most likely location of the source crater.
Aaron J. Cavosie, et al. "New clues from Earth's most elusive impact crater: Evidence of reidite in Australasian tektites from Thailand" Geology (December 20, 2017).

Ancient Beringian DNA Sheds More Light On Native American Origins

The latest New World ancient DNA results, in broad outline, reinforce the existing paradigms, but add lots of nuggets of detail.
Despite broad agreement that the Americas were initially populated via Beringia, the land bridge that connected far northeast Asia with northwestern North America during the Pleistocene epoch, when and how the peopling of the Americas occurred remains unresolved. Analyses of human remains from Late Pleistocene Alaska are important to resolving the timing and dispersal of these populations. 
The remains of two infants were recovered at Upward Sun River (USR), and have been dated to around 11.5 thousand years ago (ka). Here, by sequencing the USR1 genome to an average coverage of approximately 17 times, we show that USR1 is most closely related to Native Americans, but falls basal to all previously sequenced contemporary and ancient Native Americans. As such, USR1 represents a distinct Ancient Beringian population. 
Using demographic modelling, we infer that the Ancient Beringian population and ancestors of other Native Americans descended from a single founding population that initially split from East Asians around 36 ± 1.5 ka, with gene flow persisting until around 25 ± 1.1 ka. Gene flow from ancient north Eurasians into all Native Americans took place 25–20 ka, with Ancient Beringians branching off around 22–18.1 ka. 
Our findings support a long-term genetic structure in ancestral Native Americans, consistent with the Beringian ‘standstill model’. 
We show that the basal northern and southern Native American branches, to which all other Native Americans belong, diverged around 17.5–14.6 ka, and that this probably occurred south of the North American ice sheets. We also show that after 11.5 ka, some of the northern Native American populations received gene flow from a Siberian population most closely related to Koryaks, but not Palaeo-Eskimos, Inuits or Kets, and that Native American gene flow into Inuits was through northern and not southern Native American groups. Our findings further suggest that the far-northern North American presence of northern Native Americans is from a back migration that replaced or absorbed the initial founding population of Ancient Beringians.

Wednesday, January 3, 2018

Savannah Ecologies Of Africa, India and Eurasia Were Once Connected

The scene was set for hominin evolution on the savannah in Africa in the late Miocene era, a geological epoch that spans from 23,030,000 to 5,333,000 years ago. 
Despite much interest in the ecology and origins of the extensive grassland ecosystems of the modern world, the biogeographic relationships of savannah palaeobiomes of Africa, India and mainland Eurasia have remained unclear. Here we assemble the most recent data from the Neogene mammal fossil record in order to map the biogeographic development of Old World mammalian faunas in relation to palaeoenvironmental conditions. Using genus-level faunal similarity and mean ordinated hypsodonty in combination with palaeoclimate modelling, we show that savannah faunas developed as a spatially and temporally connected entity that we term the Old World savannah palaeobiome. The Old World savannah palaeobiome flourished under the influence of middle and late Miocene global cooling and aridification, which resulted in the spread of open habitats across vast continental areas. This extensive biome fragmented into Eurasian and African branches due to increased aridification in North Africa and Arabia during the late Miocene. Its Eurasian branches had mostly disappeared by the end of the Miocene, but the African branch survived and eventually contributed to the development of Plio–Pleistocene African savannah faunas, including their early hominins. The modern African savannah fauna is thus a continuation of the extensive Old World savannah palaeobiome.
Ferhat Kaya, et al., "The rise and fall of the Old World savannah fauna and the origins of the African savannah biome" Nature Ecology and Evolution (January 1, 2018).

Muon g-2 Measurement Underway At Fermilab

A 2001 measurement of the muon magnetic moment at Brookhaven showed a 3.5 standard deviation discrepancy between the measured value and the one predicted by the Standard Model, which has been the talk of the physics world ever since, because the muon magnetic moment (muon g-2) is sensitive to the entire spectrum of particles and forces in a model and this hints at beyond the Standard Model physics.

Fermilab commenced its experiment to repeat the Brookhaven measurement with more precision in November of 2017 following an engineering run in the summer of 2017. It will continue to take most of its data in 2018, with some additional data collection through 2020. When it is complete, the combined experimental error will be approximately a quarter of that of the Brookhaven experiment, in part, because it will collect 21 times as much data. Preliminary results that are still an improvement over the 2001 measurement may be available some time in early 2019.

This new experimental measurement, combined with increased accuracy in the calculation of the Standard Model prediction for muon g-2 which scientists have been working on intensely for the last decade and a half should definitively resolve the question of whether the muon g-2 anomaly is anything more than experimental error, and if so, how large it is, which tells us how close to the Standard Model any new physics must be.

Tuesday, January 2, 2018

SUSY Exclusions Summarized and Photoproduction of Pions

SUSY Exclusions at ATLAS

A new preprint summarizes the ATLAS SUSY exclusions to date (there are no anomalies or hints in the searches pointing to SUSY particles). 

Gluinos are excluded below about 2 TeV, while stop and sbottom squarks are excluded up to the high hundreds of GeVs.

Somewhat disappointingly, even though Figure 1 of the paper points out the one of the most important arguments for SUSY is that it modifies the beta functions of the Standard Model coupling constants (i.e. it causes Standard Model forces to become stronger or weaker at high energies in a different way that the Standard Model does), there are no reports on the measurements the LHC has made of the running of the Standard Model coupling constants with energy scale even tough it should have enough data at this point to make preliminary reporters on this question.

Pion Photoproduction

If you hit a proton with an X-ray (i.e. a high energy photon), one thing that can happen is that it can spit out a proton and a neutral pion, which in turn decays to a positron, an electron, and a photon. The CLAS experiment did this and compared the results to the predictions of the Standard Model and in particular, to the strong force part of the Standard Model called QCD.

The neutral pion is special. As the paper cited below explains in its introduction:
[T]here are properties of π0 that make this particle very special for our understanding of Quantum Chromodynamics (QCD). To name a few: it is the lightest element of all visible hadronic matter in the Universe; according to its qq¯ content the π0 has a mass much less than one would expect from a constituent quark mass, m ≈ 350 MeV and it has an extremely short life time, τ ≈ 10−16 s. Its main decay mode, π0 → γγ, with a branching ratio ≈ 99%, played a crucial role in confirming the number of colors in QCD and in establishing the chiral anomaly in gauge theories. With all this being said, the structure and properties of π0 are not completely understood.
Certain predictions of QCD were accurately reproduced. Others, based upon a Parton Distribution Function (PDF) used to make calculations in QCD which was empirically established at a lower energy scale was quite a bit off the mark, suggesting that PDFs are more energy scale dependent than expected.

While we think we know the exact "laws of the universe" for QCD, except for the exact value of some experimentally measured physical constant (especially the QCD coupling constant), the math necessary to turn those equations into actual predictions is so hard that scientists have to approximate and the task of figuring out which approximations to use in which circumstances continues to be on ongoing project established by trial and error.

The abstract of the preprint and it citation are as follows:

"Exclusive photoproduction cross sections have been measured for the process γppπ0(e+e(γ)) with the Dalitz decay final state using tagged photon energies in the range of Eγ=1.2755.425 GeV. The complete angular distribution of the final state π0, for the entire photon energy range up to large values of t and u, has been measured for the first time. The data obtained show that the cross section dσ/dt, at mid to large angles, decreases with energy as s6.89±0.26. This is in agreement with the perturbative QCD quark counting rule prediction of s7. Paradoxically, the size of angular distribution of measured cross sections is greatly underestimated by the QCD based Generalized Parton Distribution mechanism at highest available invariant energy s=11 GeV2. At the same time, the Regge exchange based models for π0 photoproduction are more consistent with experimental data."

Kunkle, et al., "Exclusive photoproduction of π0 up to large values of Mandelstam variables s,t and u with CLAS" (December 29, 2017).

The data was actually collected in 2008.