"Paleo-Asian" Ancestry In The Amazon Is Widespread In South America And Looks Comparatively Recent

The "Paleo-Asian" signal originally seen in only a couple of mostly isolated tribes deep in the source waters of the Amazon. This could have been explained as an outlier attributable to a single or couple of nuclear families at the vanguard of the Pacific route expansion (and was hard to explain any other way). New data largely rules out this hypothesis.

The authors of a new paper have with more careful examination been seen all over the place in South America. They propose an origin in the Asian source population for Pacific route migrants to the Americas in the Founding area that was absent in the portion of the Founding population that ended up in North America and Central America.

The screaming loud problem with the hypothesis that this is associated with the Founding population of the Americas is that there is material and large interpopulation and intrapopulation variability in the signal, in populations spread across South America. 

Inter-population variability could be plausible for populations in isolated Amazonian tribes, or groups with strong endogamy norms. But immense intra-population variability simply should not survive for 14,000 years (about 500 generations). The law of averages catches up with that kind of variability surprisingly quickly in the case of traits that are ancestry informative but not distinguishable as a visible phenotype without extreme population structure, which a trait spread across myriad different pre-Columbian cultures simply couldn't maintain.

Instead, the wide variability and wide geographic range points to a source of this genetic component in much more recent mariners, certainly no older than the arrival of the Paleo-Eskimo ancestors of the Na-Dene in Alaska (ca. 4500 years ago), but more likely (since this ancestry is not seen anywhere outside South America) via Polynesian mariners in the last 1500 years or less (about 30 generations or less), where solid evidence already shows sign of some slight recent admixture of South Americans into Polynesian gene pools nearest to South America, and where evidence from remains of flora and fauna native to the Americas in Polynesia and native to Polynesia on the Pacific Coast has established that some limited pre-Columbian maritime trade via the Pacific Ocean had to have taken place in about that time frame. The likely epicenter from which the admixture radiates also coincides with one of the most likely loci of South American source admixture into Polynesians ca. 1200 CE.

It is disappointing that the paper doesn't have analysis addressing this glaring and obvious issue, despite all of its sophistication in other respects.

Some thin admixture of Polynesians (the average amount of admixture from the Paleo-Asian source is on the order of 2% with wide variation plus and minus in individuals where it is present, also suggesting a minimum date of admixture of 150-180 years ago, i.e. prior to 1840-1870 CE in five or six generations, although potentially much older than that) with high levels of Papuan admixture (some Papuan admixture is present in all Polynesians) into South American societies in these much more recent time periods (but not in modern times, in order to allow for dispersal of this ancestry throughout South America and to insure that it isn't more distinctively modern in character, e.g. ruling out a source from recent Japanese migrants to Peru) could produce the observed scatter. 

It isn't obvious why this signal isn't more obviously Polynesian. And this lack of clear Polynesian genetic affinity could point to some other explanation that is still in a time frame much more recent than the Founding era of the Americas. But whatever the explanation is, it just can't have a 14,000 years old source. 

Ideally, it ought to be possible to better estimate the time frame of this admixture with linkage disequilibrium analysis, but the data may be too thin and the source population too ill defined to make that feasible. Statistical modeling of the possible variation by Monte Carlo methods with the data in this paper alone ought to be sufficient to make a decent estimate that would be much younger than what is proposed. A good benchmark that is well studied over a time scale, that is a bit shorter but on the same order of magnitude, is the population genetic history of Quebec.

Fig. 1. Relative patterns of genetic affinity of Australasians among Native American groups. (A) Maximum Z values per population interpolated with the inverse distance weighting method. (B) Distribution of all estimated Z values (y axis) for each “Z” population (x axis) as violin and box plots. In B, the black dots represent outliers, and the red dashed lines indicate the Z-value thresholds of Z = −3 and Z = 3.

The paper and its abstract are as follows:

Different models have been proposed to elucidate the origins of the founding populations of America, along with the number of migratory waves and routes used by these first explorers. Settlements, both along the Pacific coast and on land, have been evidenced in genetic and archeological studies. However, the number of migratory waves and the origin of immigrants are still controversial topics. 

Here, we show the Australasian genetic signal is present in the Pacific coast region, indicating a more widespread signal distribution within South America and implicating an ancient contact between Pacific and Amazonian dwellers. 

We demonstrate that the Australasian population contribution was introduced in South America through the Pacific coastal route before the formation of the Amazonian branch, likely in the ancient coastal Pacific/Amazonian population. 

In addition, we detected a significant amount of interpopulation and intrapopulation variation in this genetic signal in South America. This study elucidates the genetic relationships of different ancestral components in the initial settlement of South America and proposes that the migratory route used by migrants who carried the Australasian ancestry led to the absence of this signal in the populations of Central and North America.

Marcos Araújo Castro e Silva, et al., "Deep genetic affinity between coastal Pacific and Amazonian natives evidenced by Australasian ancestry" 118 (14) PNAS e2025739118 (April 6, 2021) https://doi.org/10.1073/pnas.2025739118 (Hat Tip to DDeden in the comments). Supplemental materials here. Data here.

As the body text explains:

A signal of genetic affinity between present-day and ancient natives from South America and present-day indigenous groups of South Asia, Australia, and Melanesia has been previously reported. This Australasian−Native American connection persists as one of the most intriguing and poorly understood events in human history. 

The controversial Australasian population genetic component (i.e., “Ypikuéra population” or “Y population” component) was identified exclusively in the present-day Amazonian populations suggesting at least two different founding waves leading to the formation of the people of this region. 

The first wave was inferred to be composed of direct descendants of the Beringian standstill population, and a second wave was formed by an admixed population of Beringian and southeast Asian ancestors that reached Beringia more recently. Both these populations would have settled and admixed in the Amazon region.

The contribution of an unsampled population to the autochthonous gene pool is thought to have led to the origin of the Australasian shared ancestry. In this sense, the Y population would be part of the first colonizing groups of the American continent. However, data from ancient South American samples indicated a weak Y signal around 10,000 yBP. This evidence indicates that, rather than a second wave entering South America from southeast Asia, the Y ancestry might be traced back to common ancestors of Native Americans, who lived in northeast Asia. 

Furthermore, a new line of evidence indicates that the first American clades split in East Asia, not in Beringia, which makes the gene flow of the Y ancestry from the ancestral East Asian groups even more likely. 

However, the paucity of the signal among present-day and ancient groups, along with the endemic and apparently random pattern of detection, has raised the possibility that it could be a false-positive detection, likely due to the strong genetic drift effects experienced by the Amazonian populations (and other indigenous South Americans). However, it might be the other way around, a scenario in which the signal went below the significance level in some populations, due to the high drift effects they experienced (i.e., false negatives).

We explored our dataset, which is currently the most comprehensive set of genomic data from South American populations (383 individuals; 438,443 markers), to shed light on this question. 

. . .

Our results showed that the Australasian genetic signal, previously described as exclusive to Amazonian groups, was also identified in the Pacific coastal population, pointing to a more widespread signal distribution within South America, and possibly implicating an ancient contact between Pacific and Amazonian dwellers. In addition, a significant amount of interpopulation and intrapopulation variation of this genetic signal was detected.

To test the existence of this excess allele sharing, we calculated the D(Mbuti, Australasian; Y, Z) statistic for every pair of Y and Z indigenous groups or individuals in our dataset, where “Australasian” is also iterated over the Australasian groups, namely Australian (and Australian.DG), Melanesian, Onge (i.e., ONG.SG), and Papuan. In the tests between groups, signal detection was reproduced in Karitiana and Suruí (Amazonia), but it was also observed in Chotuna (Mochica descendants from the Pacific coast), Guaraní Kaiowá (central west Brazil), and Xavánte (Central Brazilian Plateau). 

When we used the maximum unrelated set of individuals, the signal lost significance level in Karitiana, Suruí, and Guaraní Kaiowá . However, the signal was still evident in the Pacific coast population and in the central Brazilian natives. 

. . . 

the loss of signal significance upon the shift from the complete set to the maximum unrelated set of samples was caused by the exclusion of specific individuals with higher levels of allele sharing with Australasians rather than by the removal of a bias caused by the relatedness among the tested samples in the first place. . . . .

This provides strong evidence that a significant variability of this signal exists not only at an interpopulation level but also between individuals from the same populations. These results suggest that the intrapopulation variability of this signal is not rare and is observed in several groups (Apalai, Guaraní Nãndeva, Karitiana, Munduruku, Parakanã, and Xavánte). Most significant tests detected this excess signal in Tupí-speaking individuals, but the signal was also detected in individuals from every major linguistic group and, at the same time, presented a widespread geographic distribution within South America. Conversely, a considerable number of samples were inferred to have a deficit of allele sharing with Australasians. 

Strikingly, the individual PAR137 (Parakanã) presented an extremely high proportion of significant tests (31.64%), indicating a relative deficit. This individual is not an outlier neither in the principal component analysis of the Native American samples, nor regarding its missingness rate, nor in a multidimensional scaling (MDS) of pairwise genetic distances between samples in the unrelated and unadmixed subset. Besides, the distribution of Y-population ancestry among present-day indigenous groups of South America showed no relationship with ethnolinguistic diversity or geographic location. 

. . .

Different migration routes to the South American region have been previously proposed and evidenced. Archeological and genetic data demonstrated that both routes, Pacific coastal and inland, were likely used by the first migrants. 

Our models point to an ancient genetic affinity between the Pacific coast and Amazonian populations that could be explained by the presence of Y ancestry in both geographic regions. 

In addition, this shared ancestry seems to precede the separation of the Pacific and Amazon branches, showing an entry through the west coast, followed by successive events of genetic drift in the Brazilian populations. This genetic evidence for the presence of Y ancestry on the South American Pacific coast indicates that this ancestry likely reached this region through the Pacific coastal route, and therefore could explain absence of this genetic component in the populations of North and Central America studied so far.

Previous Posts At This Blog

The following previous posts at this blog discuss the Paleo-Asian ancestry in the Americas issue or issues of pre-Columbian contact with Oceania and Asia, at least in passing:

* Ancient DNA Tweaks Understanding Of American Founding Population's Origins (UPDATED October 15, 2020)

* DNA Evidence Of Polynesian Admixture With Native Americans Ca. 1200 CE (July 9, 2020).

* How To Migrate To America Without Leaving Much Of A Genetic Trace (December 7, 2018).

* 14,000 Year Old Fishing Village Unearthed In British Columbia (November 29, 2018).

* Ancient DNA From Patagonia Supports Paradigm (April 9, 2018).

* Ancient DNA Refines New World Settlement Paradigm (October 15, 2017).

* Pre-Columbian European Admixture In Northern Chile? (May 10, 2017).

* Undeniable Evidence Of Austronesian-South American Pre-Columbian Contact (January 27, 2017).

* The Na-Dene Have Paleo-Eskimo Ancestors (September 14, 2016).

* A Teaser and Recap Of Recent Developments Post UPDATED (August 12, 2016).

* Paleo-Asians Part II Some Observations And Preliminary Conclusions (August 4, 2015).

* Paleo-Asians Part I Overview, Definitions, Archaic Hominins and the Jomon (July 23, 2015).

* Kennewick Man Has Native American DNA And Confirms Paradigm (January 19, 2015).

* More Evidence Of Pre-Columbian Contact With Asia (October 28, 2014).

The Latest Basque Genetics Paper

A new paper on Basque genetics is out with both ancient and modern samples, honing in on the geographically localized heterogeneity of Basque genetics even within Basque country in Northern Spain and Southeastern France. Razib blogs it here without any real commentary except from his readers. 

The paper shows that the Basques who speak the Basque language are indeed genetically distinct from their neighbors in Iberia and Southern France, with their immediately adjacent close neighbors, called "Peri-Basque" in the paper, being intermediate). 

The Basque lack the genetic contributions of the Iron Age Romans and from the Moors in the Middle Ages is largely found in other Iberians. It also shows strongly small scale geographic variation in Basque genetics from subregion to subregion of Basque country.

It does not appear to show any real Basque distinctiveness attributable to earlier eras, although the paper slightly hedges its bets on that score. The lack of pre-Iron Age genetic differentiation is a finding that I am skeptical of given prior publications and the historical and linguistic context, although I don't rule it out, out of hand. 

At least some Indo-European influences arrived in Iberia in the Bronze Age, not the Iron Age, and the Basque people obvious avoided cultural domination at that time, even though this paper's genetic analysis doesn't real reveal any genetic evidence in modern Basque people that this happened.

Certainly, the Romans are the source of all of the Romance languages spoken in Iberia today. But the pre-Roman linguistic character of Iberia is muddy, with Celtic languages present in or near parts of Iberia in pre-Roman times as well, for example, and the Bell Beaker phenomena originating there.

My ambivalence is, in part, because there is good reason based upon historical and linguistic evidence, to think that much more of Iberia was Vasconic in the pre-Roman era than it is today, with sister languages of the Basque language's going extinct in the face of Roman influence. It could be that influences distinct to Bronze Age Vasconic people are invisible because, apart from the Basque people, Iberian Vasconic people may have been thoroughly integrated into the Iberian general population in 85 or so generation that followed from Roman conquest until the modern samples were taken.

Another important conclusion reached, contrary to some of my conjectures in the past on the matter, is that there is no discernible Caucasian/Iranian farmer or Caucasian/Iranian hunter-gatherer ancestry found in the Basque population (or in the general Iberian population).

Image from Broushaki et al. (2016).

While it is well known that language shift can occur in a population whose population genetics are unchanged, the lack of a Caucasian/Iranian farmer genetic signal in Iberians still disfavors the possibility that Basque is a language that arrived in Iberian in the Copper Age/early Bronze Age from a Minoan/Hattic/Hurrian/Caucasian, pre-Indo-European Iranian, or Harappan source (all of which would be expected to have some of this genetic signal), or at least, that any migrants from these societies were few in number, making the likelihood that they brought about language shift in the Neolithic societies in which they arrived smaller. This component isn't entirely absent from Copper Age and Bronze Age Pontic Caspian steppe peoples (who did leave a discernible genetic impact on Iberians), but as Davidski notes in  recent post at Eurogenes, it was a quite dilute and minor component.

Instead, this data point tends to favor (by process of elimination) the hypothesis that that Vasconic languages are derived from the first farmers of Iberia and its vicinity, which in turn would have been derived from the languages of the Western Anatolian first farmers who expanded into Europe in the European Neolithic Revolution, primarily in a Northern Linear Pottery Culture and cultures derived from it, and in a Mediterranean coastal Cardial Pottery culture and cultures derived from it, which would be the most plausible source for most Iberian farmers. 

The paper is thinner on analysis and context that might be hoped given the depth of the literature on this particular matter, and does less to leverage its ancient DNA samples than it could, so I'll provide some context in this post to supplement it.

Iberia's Neolithic Revolution showed more internal regional variation than most of Europe, where most regions saw only a single wave of first farmers, did:

In the 6th millennium BC, Andalusia experiences the arrival of the first agriculturalists. Their origin is uncertain (though North Africa is a serious candidate) but they arrive with already developed crops (cereals and legumes). The presence of domestic animals instead is unlikely, as only pig and rabbit remains have been found and these could belong to wild animals. They also consumed large amounts of olives but it's uncertain too whether this tree was cultivated or merely harvested in its wild form. Their typical artifact is the La Almagra style pottery, quite variegated.

The Andalusian Neolithic also influenced other areas, notably Southern Portugal, where, soon after the arrival of agriculture, the first dolmen tombs begin to be built c. 4800 BC, being possibly the oldest of their kind anywhere.

C. 4700 BC Cardium pottery Neolithic culture (also known as Mediterranean Neolithic) arrives to Eastern Iberia. While some remains of this culture have been found as far west as Portugal, its distribution is basically Mediterranean (Catalonia, Valencian region, Ebro valley, Balearic islands).

The interior and the northern coastal areas remain largely marginal in this process of spread of agriculture. In most cases it would only arrive in a very late phase or even already in the Chalcolithic age, together with Megalithism. 

The location of Perdigões, in Reguengos de Monsaraz, is thought to have been an important location. Twenty small ivory statues dating to 4,500 years BP have been discovered there since 2011. It has constructions dating back to about 5,500 years. It has a necropolis. Outside the location there is a cromlech. The Almendres Cromlech site, in Évora, has megaliths from the late 6th to the early 3rd millennium BC. The Anta Grande do Zambujeiro, also in Évora, is dated between the early 4th and the mid 3rd millennium BC. The Dolmen of Cunha Baixa, in Mangualde Municipality, is dated between 3000 and 2500 BC. The Cave of Salemas was used as a burial ground during the Neolithic.

What was going on in Iberia in the Copper Age?

The Chalcolithic or Copper Age is the earliest phase of metallurgy. Copper, silver and gold started to be worked then, though these soft metals could hardly replace stone tools for most purposes. The Chalcolithic is also a period of increased social complexity and stratification and, in the case of Iberia, that of the rise of the first civilizations and of extensive exchange networks that would reach to the Baltic and Africa. The conventional date for the beginning of Chalcolithic in Iberia is c. 3000 BC. In the following centuries, especially in the south of the peninsula, metal goods, often decorative or ritual, become increasingly common. Additionally there is an increased evidence of exchanges with areas far away: amber from the Baltic and ivory and ostrich-egg products from Northern Africa.

The Beaker culture was present in Iberia during the Chalcolithic. Gordon Childe interpreted the presence of its characteristic artefact as the intrusion of "missionaries" expanding from Iberia along the Atlantic coast, spreading knowledge of Mediterranean copper metallurgy. Stephen Shennan interpreted their artefacts as belonging to a mobile cultural elite imposing itself over the indigenous substrate populations. Similarly, Sangmeister (1972) interpreted the "Beaker folk" (Glockenbecherleute) as small groups of highly mobile traders and artisans. Christian Strahm (1995) used the term "Bell Beaker phenomenon" (Glockenbecher-Phänomen) as a compromise in order to avoid the term "culture".

The Bell Beaker artefacts at least in their early phase are not distributed across a contiguous areal as is usual for archaeological cultures, but are found in insular concentrations scattered across Europe. Their presence is not associated with a characteristic type of architecture or of burial customs. However, the Bell Beaker culture does appear to coalesce into a coherent archaeological culture in its later phase.

More recent analyses of the "Beaker phenomenon", published since the 2000s, have persisted in describing the origin of the "Beaker phenomenon" as arising from a synthesis of elements, representing "an idea and style uniting different regions with different cultural traditions and background. "Archaeogenetics studies of the 2010s have been able to resolve the "migrationist vs. diffusionist" question to some extent. The study by Olalde et al. (2017) found only "limited genetic affinity" between individuals associated with the Beaker complex in Iberia and in Central Europe, suggesting that migration played a limited role in its early spread from Iberia. However, the same study found that the further dissemination of the mature Beaker complex was very strongly linked to migration. The spread and fluidity of the Beaker culture back and forth between the Rhine and its origin source in the peninsula may have introduced high levels of steppe-related ancestry, resulting in a near-complete transformation of the local gene pool within a few centuries, to the point of replacement of about 90% of the local Mesolithic-Neolithic patrilineal lineages.

The origin of the "Bell Beaker" artefact itself has been traced to the early 3rd millennium. The earliest examples of the "maritime" Bell Beaker design have been found at the Tagus estuary in Portugal, radiocarbon dated to c. the 28th century BC. The inspiration for the Maritime Bell Beaker is argued to have been the small and earlier Copoz beakers that have impressed decoration and which are found widely around the Tagus estuary in Portugal. Turek has recorded late Neolithic precursors in northern Africa, arguing the Maritime style emerged as a result of seaborne contacts between Iberia and Morocco in the first half of the third millennium BCE. In only a few centuries of their maritime spread, by 2600 BC. they had reached the rich lower Rhine estuary and further upstream into Bohemia and beyond the Elbe where they merged with Corded Ware culture, as also in the French coast of Provence and upstream the Rhone into the Alps and Danube.

A significant Chalcolithic archeological site in Portugal is the Castro of Vila Nova de São Pedro. Other settlements from this period include Pedra do Ouro and the Castro of Zambujal. Megaliths were created during this period, having started earlier, during the late 5th, and lasting until the early 2nd millennium BC. The Castelo Velho de Freixo de Numão, in Vila Nova de Foz Côa Municipality, was populated from about 3000 to 1300 BC. The Cerro do Castelo de Santa Justa, in Alcoutim, is dated to the 3rd millennium BC, between 2400 and 1900 BC.

It is also the period of the great expansion of megalithism, with its associated collective burial practices. In the early Chalcolithic period this cultural phenomenon, maybe of religious undertones, expands along the Atlantic regions and also through the south of the peninsula (additionally it's also found in virtually all European Atlantic regions). In contrast, most of the interior and the Mediterranean regions remain refractary to this phenomenon.

Another phenomenon found in the early chalcolithic is the development of new types of funerary monuments: tholoi and artificial caves. These are only found in the more developed areas: southern Iberia, from the Tagus estuary to Almería, and SE France.

Eventually, c. 2600 BC, urban communities began to appear, again especially in the south. The most important ones are Los Millares in SE Spain and Zambujal (belonging to Vila Nova de São Pedro culture) in Portuguese Estremadura, that can well be called civilizations, even if they lack of the literary component.

Extent of the Beaker culture

It is very unclear if any cultural influence originated in the Eastern Mediterranean (Cyprus?) could have sparked these civilizations. On one side the tholos does have a precedent in that area (even if not used yet as tomb) but on the other there is no material evidence of any exchange between the Eastern and Western Mediterranean, in contrast with the abundance of goods imported from Northern Europe and Africa.

Since c. 2150 BC, the Bell Beaker culture intrudes in Chalcolithic Iberia. After the early Corded style beaker, of quite clear Central European origin, the peninsula begins producing its own types of Bell Beaker pottery. Most important is the Maritime or International style that, associated especially with Megalithism, is for some centuries abundant in all the peninsula and southern France.

Since c. 1900 BC, the Bell Beaker phenomenon in Iberia shows a regionalization, with different styles being produced in the various regions: Palmela type in Portugal, Continental type in the plateau and Almerian type in Los Millares, among others. 

Our knowledge of the cultures present in Iberia by the Bronze Age is patchy.

The picture is clarified somewhat, however, by the eve of Bronze Age collapse.

Eventually, before Roman influence arrived in Iberia, however, most of the region was Celtic (and associated with this Indo-European linguistic family). This was an early Iron Age event:

The Iron Age in the Iberian peninsula has two focuses: the Hallstatt-related Iron Age Urnfields of the North-East and the Phoenician colonies of the South.

During the Iron Age, considered the protohistory of the territory, the Celts came, in several waves, starting possibly before 600 BC.

The Southwest Paleohispanic script, also called Tartessian, present in the Algarve and Lower Alentejo from about the late 8th to the 5th century BC, is possible the oldest script in Western Europe and it could have come from the Eastern Mediterranean, perhaps from Anatolia or Greece.

Since the late 8th century BC, the Urnfield culture of North-East Iberia began to develop Iron metallurgy and, eventually, elements of the Hallstatt culture. The earliest elements of this culture were found along the lower Ebro river, then gradually expanded upstream to La Rioja and in a hybrid local form to Alava. There was also expansion southwards into Castelló, with less marked influences reaching further south. Additionally, some offshoots have been detected along the Iberian Mountains, possibly a prelude to the formation of the Celtiberi.

During this period, the social differentiation became more visible with evidence of local chiefdoms and a horse-riding elite. It is possible that these transformations represent the arrival of a new wave of cultures from central Europe. From these outposts in the Upper Ebro and the Iberian mountains, Celtic culture expanded into the plateau and the Atlantic coast. Several groups can be described: 

* The Bernorio-Miraveche group (northern Burgos and Palencia provinces), that would influence the peoples of the northern fringe. 

* The north-west Castro culture, in today's Galicia and northern Portugal, a Celtic culture with peculiarities, due to the persistence of aspects of an earlier Atlantic Bronze Age culture. 

* The Duero group, possibly the precursor of the Celtic Vaccei. 

* The Cogotas II culture, likely precursor of the Celtic or Celtiberian Vettones (or a pre-Celtic culture with substantial Celtic influences), a markedly cattle-herder culture that gradually expanded southwards into what is today's Extremadura. 

* The Lusitanian culture, the precursor of the Lusitani tribe, located in what is today's central Portugal and Extremadura in western Spain, is generally not considered Celtic since the Lusitanian language does not meet some the accepted definitions of a Celtic language. Its relationship with the surrounding Celtic culture is unclear. Some believe it was essentially a pre-Celtic Iberian culture with substantial Celtic influences, while others argue that it was an essentially Celtic culture with strong indigenous pre-Celtic influences. There have been arguments for classifying its language as either Italic, a form of archaic Celtic, or proto-Celtic.

All these Indo-European groups have some common elements, like combed pottery since the 6th century and uniform weaponry.

After c. 600 BC, the Urnfields of the North-East were replaced by the Iberian culture, in a process that wasn't completed until the 4th century BC.

Approximate extent of the Celts c. 400 BCE

However: 

After c. 600 BC, the Urnfields of the North-East were replaced by the Iberian culture, in a process that wasn't completed until the 4th century BC. This physical separation from their continental relatives would mean that the Celts of the Iberian peninsula never received the cultural influences of La Tène culture, including Druidism.

The linguistic picture isn't really clearly documented until the eve of Roman conquest around 300 BCE, with the Iberian language probably sharing a linguistic family relationship with the Basque language. 

The linguistic classification of the Tartessian language is controversial:

Tartessian is generally left unclassified for lack of data or proposed to be a language isolate for lack of connections to the Indo-European languages. Some Tartessian names have been interpreted as Indo-European, more specifically as Celtic. However, the language as a whole remains inexplicable from the Celtic or Indo-European point of view; the structure of Tartessian syllables appears to be incompatible with Celtic or even Indo-European phonetics and more compatible with Iberian or Basque; all Celtic elements are thought to be borrowings by some scholars.

Since 2009, John T. Koch has argued that Tartessian is a Celtic language and that the texts can be translated. Koch's thesis has been popularised by the BBC TV series The Celts: Blood, Iron and Sacrifice and the associated book by Alice Roberts.

However, his proposals have been regarded with scepticism by academic linguists and the script, which is "hardly suitable for the denotation of an Indo-European language[,] leaves ample room for interpretation". In 2015, Terrence Kaufman published a book that suggested that Tartessian was a Celtic language but written using a script devised initially for a Vasconic "Hipponic" language (numerous SW placenames in -i(p)po(n)) although there are no extant inscriptions in such a language using the Tartessian script.

The Tartessian culture appears to be the first Iberian culture in which there is major use of cattle:

The name Tartessian, when applied in archaeology and linguistics does not necessarily correlate with the semi-mythical city of Tartessos but only roughly with the area where it is typically assumed it should have been located.

The Tartessian culture of southern Iberia actually is the local culture as modified by the increasing influence of eastern Mediterranean elements, especially Phoenician. Its core area is Western Andalusia, but soon extends to Eastern Andalusia, Extremadura and the Lands of Murcia and Valencia, where a Tartessian complex, rooted in the local Bronze cultures, is in the last stages of the Bronze Age (ninth-eighth centuries BC) before Phoenician influences can be seen clearly.

The full Tartessian culture, beginning c.720 BC, also extends to southern Portugal, where is eventually replaced by Lusitanian culture. One of the most significant elements of this culture is the introduction of the potter's wheel, that, along with other related technical developments, causes a major improvement in the quality of the pottery produced. There are other major advances in craftsmanship, affecting jewelry, weaving and architecture. This latter aspects is especially important, as the traditional circular huts were then gradually replaced by well finished rectangular buildings. It also allowed for the construction of the tower-like burial monuments that are so typical of this culture.

Agriculture also seems to have experienced major advances with the introduction of steel tools and, presumably, of the yoke and animal traction for the plough. In this period it's noticeable the increase of cattle accompanied by some decrease of sheep and goat types.

Another noticeable element is the major increase in economical specialization and social stratification. This is very noticeable in burials, with some showing off great wealth (chariots, gold, ivory), while the vast majority are much more modest. There is much diversity in burial rituals in this period but the elites seem to converge in one single style: a chambered mound. Some of the most affluent burials are generally attributed to local monarchs.

Some of the key illustrations from the new Basque genetics paper follow:

The paper says this in its discussion section:

[O]ur analyses support the notion that the genetic uniqueness of Basques cannot be attributed to a different origin relative to other Iberian populations but instead to a reduced and irregular external gene flow since the Iron Age[.] The observed clines of postIron Age gene flow in the region suggest that the specific genetic profile of Basques might be explained by the lack of recent gene flow received. Our analyses confirm that Basques were influenced by the major migration waves in Europe until the Iron Age, in a similar pattern as their surrounding populations. 

At that time, Basques experienced a process of isolation, characterized by an extremely low admixture with the posterior population movements that affected the Iberian Peninsula, such as the Romanization or the Islamic rule, as observed in the present genetic landscape. 

This does not exclude plausible previous periods of isolation, as attested by the presence of short ROHs and small Ne values that support signals of ancient inbreeding in the region, even higher than in Sardinia, which is suggested to be isolated after Neolithic times. Thus, the increase of the Ne observed only in the external groups about 1,000 generations ago might be potentially linked to the role of the Franco-Cantabrian region as glacial refugium during LGM periods and the subsequent expansion. 

Although our results support the genetic continuity from the Iron Age in most of the present day Basques, those located in the periphery of the Basque core area show signals of contacts compatible with the Roman Empire presence in the Iberian Peninsula. These results are in agreement with archaeological and historical records. An important presence of the Roman Empire has been reported in the whole Franco-Cantabrian region, but the scholars suggest a much higher impact in the peripheral areas of the southern side, specially Nafarroa and Araba. Otherwise, North African influence only fit the models where southern and northwestern Iberians are included. This confirms the reduced gene flow between the eastern and northern areas of the Iberian Peninsula with the North African incomers during the Islamic rule, as already reported by using uniparental markers and more recently through genome-wide data and haplotype-based methods.

The paper and its abstract are as follows:

Basques have historically lived along the Western Pyrenees, in the Franco-Cantabrian region, straddling the current Spanish and French territories. Over the last decades, they have been the focus of intense research due to their singular cultural and biological traits that, with high controversy, placed them as a heterogeneous, isolated, and unique population. Their non-Indo-European language, Euskara, is thought to be a major factor shaping the genetic landscape of the Basques. Yet there is still a lively debate about their history and assumed singularity due to the limitations of previous studies. 

Here, we analyze genome-wide data of Basque and surrounding groups that do not speak Euskara at a micro-geographical level. A total of
629,000 genome-wide variants were analyzed in 1,970 modern and ancient samples, including 190 new individuals from 18 sampling locations in the Basque area. For the first time, local- and wide-scale analyses from genome-wide data have been performed covering the whole Franco-Cantabrian region, combining allele frequency and haplotype-based methods.

Our results show a clear differentiation of Basques from the surrounding populations, with the non-Euskara-speaking Franco-Cantabrians located in an intermediate position. Moreover, a sharp genetic heterogeneity within Basques is observed with significant correlation with geography. 

Finally, the detected Basque differentiation cannot be attributed to an external origin compared to other Iberian and surrounding populations. Instead, we show that such differentiation results from genetic continuity since the Iron Age, characterized by periods of isolation and lack of recent gene flow that might have been reinforced by the language barrier.

Frederic Bauduer, et al., "Genetic origins, singularity, and heterogeneity of Basques" 31 Current Biology 1-11 (May 24 2021) (online ahead of publication). doi.org/ 10.1016/j.cub.2021.03.010

Cultural Traits Discernible From Folklore Are Enduring And Relevant

While folklore and legendary history are generally not literally true accounts of the past, viewed properly, they shed light on the culture that created them in ways that have enduring relevance in the societies that have preserved it.

Folklore is the collection of traditional beliefs, customs, and stories of a community passed through the generations by word of mouth. We introduce to economics a unique catalogue of oral traditions spanning approximately 1,000 societies. 

After validating the catalogue’s content by showing that the groups’ motifs reflect known geographic and social attributes, we present two sets of applications. 

First, we illustrate how to fill in the gaps and expand upon a group’s ethnographic record, focusing on political complexity, high gods, and trade. 

Second, we discuss how machine learning and human-classification methods can help shed light on cultural traits, using gender roles, attitudes towards risk, and trust as examples. Societies with tales portraying men as dominant and women as submissive tend to relegate their women to subordinate positions in their communities, both historically and today. More risk-averse and less entrepreneurial people grew up listening to stories where competitions and challenges are more likely to be harmful than beneficial. Communities with low tolerance towards antisocial behavior, captured by the prevalence of tricksters getting punished, are more trusting and prosperous today. 

These patterns hold across groups, countries, and second-generation immigrants. Overall, the results highlight the significance of folklore in cultural economics, calling for additional applications.

Stelios Michalopoulos & Melanie Meng Xue, "Folklore" Quarterly Journal of Economics, forthcoming.

Things That Make You Think The Standard Model Is True

It is easy to forget just how stunning accurate and predictive what we already know about fundamental physics is, as we obsess over the handful of moderate tensions between experiment and prediction that are outstanding. This post discusses one random example of this reality.

One of the things that the Standard Model of Particle Physics predicts with great precision is how often unstable hadrons (i.e. composite particles made up of quarks such as the positively charge kaons, made up of an up quark and an anti-strange quark, studied in the paper below) decay into other particles (in the paper below, a charged pion, made up of an up quark and an anti-down quark, and a neutrino-antineutrino pair). 

There are hundreds of different possible hadrons, each with several main decay paths and many more rare ones each, whose frequency is predicted in each case.

The Prediction

The charged kaon to charged pions neutrino antineutrino decay was calculated in a 2015 paper to happen in the Standard Model  between 64 and 104 times per trillion charged kaon decays (with 95% confidence intervals) with a best fit value of 84 times per trillion. 

It is rare because the process is only possible when it occurs through multiple intermediate "virtual" steps called "electroweak box and penguin diagrams" the most important of which involve top quarks, that cancel out leaving no direct trace in the end products. This decay can't happen at "tree level" without these "loop effects".

In their sample of about  120 billion charged kaon decays for which they were able to characterize decay products, that corresponds to 10 events (net of background events) predicted by the Standard Model. The error budget in the predicted Standard Model calculation is as follows:

V(cb) and γ are physical constants that are part of the CKM matrix, representing the probability of transitions from bottom quarks to charm quarks in weak force mediated transitions (the constant is 0.0410 ± 0.0014, and the probability of that transition is the square of that constant) and one of the angles of its unitary triangle which is a function of the various CKM matrix elements taken as a whole (which is 73.2º + 6.3º - 7.0º).

Keep in mind, that this is a genuine ex ante prediction. While the calculation was done in 2015 (still prior to the data collection), the equations used were derived in the early 1980s, and the physical constants used were all determined experimentally in completely independent experiments, done long in advance and refined from time to time in independent experiments. Yet, this tiny needle in a haystack measurement is still consistent with the prediction, and was first possible with data collected in 2016-2018.

The Result

This decay has indeed been observed (the odds that this is due simply to random chance fluctuations in background processes is 34 per 100,000) and happens at a frequency between 36 and 188 time per trillion charged kaon decays (with 95% confidence intervals) with a best fit value of 106 times per trillion, based upon an observed 20 events with a background expected to average 7 events, leaving a signal of 13 events (compared to the predicted 10 event signal). This number of events is consistent with the Standard Model prediction at the two standard deviation level.

The Paper

As the introduction to the paper explains:

The K^+ → π +νν¯ decay is a Flavour Changing Neutral Current (FCNC) process that proceeds at the lowest order in the Standard Model (SM) through electroweak box and penguin diagrams, both dominated by t-quark exchange. The quadratic Glashow-Iliopoulos-Maiani (GIM) mechanism and the transition from a top to a down quark make this process extremely rare. Using tree-level elements of the Cabibbo-Kobayashi-Maskawa (CKM) matrix as external inputs, the SM predicts the branching ratio to be BR = (8.4 ± 1.0) × 10^−11, where the uncertainty is dominated by those of the CKM parameters V(cb) and γ. The intrinsic theoretical uncertainty is 3.6%, related to the uncertainty of the NLO (NNLO) QCD corrections to the top (charm) quark contribution and NLO electroweak corrections. The uncertainties due to the hadronic matrix element governing the K–π transition are negligible, because they are evaluated using the precisely measured branching ratio of K^+ → πº e^+ ν, corrected for isospin-breaking and non-perturbative effects[.]

The paper and its abstract are as follows:

The NA62 experiment reports the branching ratio measurement BR(K+ → π +νν¯) = (10.6 +4.0 −3.4 |stat ± 0.9syst) × 10−11 at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016–2018. This provides evidence for the very rare K+ → π +νν¯ decay, observed with a significance of 3.4σ. The experiment achieves a single event sensitivity of (0.839±0.054)×10−11, corresponding to 10.0 events assuming the Standard Model branching ratio of (8.4±1.0)×10−11. 

This measurement is also used to set limits on BR(K+ → π +X), where X is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample.

NA62 Collaboration "Measurement of the very rare K+→π+νν¯ decay" arXiv 2103.15389 (March 29, 2021).

Footnote on Dark Matter

The paper also sets strict constraints on potential number of spin-0 dark matter candidates "X" with masses of up to about twice the mass of a pion (260 MeV) that can be produced in charged kaon decays that could be produced in this process:

This result is also interpreted in the framework of a search for a feebly interacting scalar or pseudo-scalar particle X, produced in the decay K^+ → π +X with the same experimental signature as the dominant background process K^+ → π +νν¯. Upper limits on the branching ratio at 90% CL of 3–6 ×10^−11 are obtained for m(X) masses in the range 0–110 MeV/c^2 and 1 × 10^−11 for mX masses in the range 160–260 MeV/c^2 . A particular model where X is a dark sector scalar mixing with the Higgs boson has been explored, setting more stringent constraints on the allowed region in the plane (m(X), sin2(θ)), where θ is the mixing angle.

This tiny frequency of hypothetical dark matter particle production is far too low to be a promising dark matter candidate by this production method.

Burushaski

One possibility for the language or language family that once included Harappan is that it continues to survive today in the form of a language isolate. (Previous analysis at this blog here). 

If that were the case, the Burushaski language would be the most plausible candidate, by virtue of location (in Kashmir), established antiquity (from references in old Tibetan texts), due to the presence of retroflex consonants, and because all other plausible candidates (Indo-European, Dravidian, Munda, and Uralic) can be ruled out. Pre-fixing was probably part of the Harappan language and is present in Burushaski as well, although it also has suffixes and doesn't necessary pre-fix in the same way. The fact that Burushaski has some ergative features and that it makes an animate/inanimate distinction also supports the hypothesis, although it does not apparently use the k- prefix to make that distinction.

There is one other language isolate in India, the Nahali language, but its location in West Central India is less of a good fit, and its antiquity is in doubt (Nahali may have a "thieves' cant" with roots in a Munda language developed in the 1800s for the purpose of being indecipherable to outsiders.) It also has retroflex consonants (an areal feature of many South Asian languages, likely derived from contact with Harappan).

As Wikipedia notes:

The Harappan language is the unknown language or languages of the Bronze Age (2nd millennium BC) Harappan civilization (Indus Valley Civilization, or IVC). The language being unattested in any readable contemporary source, hypotheses regarding its nature are reduced to purported loanwords and substratum influence, notably the substratum in Vedic Sanskrit and a few terms recorded in Sumerian cuneiform (such as Meluhha) . . . There are a handful of possible loanwords from the language of the Indus Valley Civilization. Sumerian Meluhha may be derived from a native term for the Indus Valley Civilization, also reflected in Sanskrit mleccha meaning foreigner and Witzel (2000) further suggests that Sumerian GIŠšimmar (a type of tree) may be cognate to Rigvedic śimbala and śalmali (also names of trees).

I don't have any stronger evidence in favor of the hypothesis, but because other possibilities seem unlikely, it deserves more attention. Presumably, efforts have been made to show lexical connections that have failed to provide strong evidence of a connection, but I don't know that for a fact.

Responding To The 5.2 Kya Event In Anatolia

There aren't many studies demonstrating the impact of the 5.2 kiloyear climate event on historic communities of people, in part, because the civilizations impacted by it at the Neolithic-Copper Age transition didn't have the same scale of urban areas, empires, architecture and sophisticated goods to collapse from, and writing was much more limited then, making the impact less obvious. 

But this study deserves kudos for using clever methods to observe these subtle impacts on human communities on a quite fine grained time scale which other methods can't always resolve nearly as finely.

Just as the 4.2 kya event was pivotal in ushering in the Bronze Age and creating a political vacuum into which Indo-Europeans could expand in Europe, Central Asia and South Asia, the 5.2 kya event was pivotal in creating a political vacuum in Neolithic society into which copper age cultures could expand. 

This (or the 5.9 kya event) is probably the climate event that was the proximate cause of the demographic transition from the Sardinian-like Anatolian first farmers of the Fertile Crescent Neolithic Revolution to copper age people with a different genetic makeup who migrated to Anatolia from elsewhere in the West Asian highlands who partially replaced them in Anatolia.

It is also one of the first documented iterations of a pattern that would repeat itself many times in history. When rain is ample and temperatures are comfortable, agriculture flourishes and sophisticated sedentary civilizations arise. When drought strikes and it gets too hot or too cold, herding civilizations replace the farming civilizations that flourished in better times.

"People would build a mud brick structure, and over the years the structure is either abandoned or collapses and the people just build on top of it," Smith says. "Eventually these villages look like they have been built on hills, but they're really just occupations going up and up."

Just as the occupants built new layers up, the archaeologists excavate down to get a glimpse of history and how lives changed over the millennia. Within the layers, archaeobotanists like von Baeyer and Smith look for ancient plant remains; for instance, intentionally or unintentionally charred plant matter. Though wood was often used, much can be learned by looking at the remains of fires fueled by livestock dung, says Smith: "The dung contains seeds that give clues about what the animals were eating." 

. . .

The focus was on a time period called the Late Chalcolithic, roughly 3700-3200 years before the common era (BCE). By referencing paleo-climatic data and Steadman's very detailed phasing at Çadır Höyük, the researchers were able to discern how lifestyles changed as the climate rapidly shifted in what is called the 5.2 kya event, an extended period of aridity and drought at the end of the fourth millennium BCE.

With climate change, there are lots of strategies that can be used to adapt says Smith, "They could have intensified, diversified, extensified, or abandoned the region entirely. In this case they extensified the area of land used and diversified the herds of animals they relied upon."

Zooarchaeologists on the site examined the bones to further demonstrate the shift in the types of animals herded, while the seeds from the dung-fueled fires at the dig site gave clues to what the animals were eating.

Smith says, "We know they were herding cattle, sheep, goats, and pigs, and we saw a shift to animals that are grazers. They all have a different diet, and by diversifying you are maximizing the range of potential calories that can eventually be consumed by humans."

By employing this mixed strategy, the people of Çadır Höyük were ensuring their survival as the climate became increasingly dry. Smith says that at the same time they continued to grow wheat, barley, chickpeas, and lentils, among other crops for humans, while the animals grazed on crops not suitable for human consumption -- a strategy to maximize resources and resilience.

From here. The paper and its abstract are as follows:

This study examines how the population at Çadır Höyük on the north central Anatolian plateau modified agricultural and fuel use practices in response to rapid social and environmental change between 3600 and 2900 BCE (Late Chalcolithic and Transitional to Early Bronze periods). 

Using descriptive and multivariate statistics to explore data from 60 archaeobotanical samples spanning three periods of occupation (3600–3200 BCE, 3300–3100 BCE, and 3100–2900 BCE) the results reveal that the inhabitants of Çadır relied heavily on barley, emmer, lentils, and flax throughout the Late Chalcolithic. Both dung and wood were used as fuel, although dung fuel appears to have been preferentially used. 

The most significant change throughout this period was a shift from foddering animals to grazing animals on the steppe. This shift corresponded with the 5.2 kya event, a period of increased aridity at the very end of the 4th millennium BCE. By diversifying their agricultural strategies to more risk adverse practices, the population at Çadır demonstrated their ability to be resilient in the face of climate change.

Madelynn von Baeyer, Alexia Smith, Sharon R. Steadman. "Expanding the plain: Using archaeobotany to examine adaptation to the 5.2 kya climate change event during the Anatolian Late Chalcolithic at Çadır Höyük." 36 Journal of Archaeological Science: Reports 102806 (2021). DOI: 10.1016/j.jasrep.2021.102806

Neutrino Physics At Moriond

I've clipped key conclusions from many of the leading neutrino physics presentations at Moriond 2021, one of the biggest physics conferences of the year, this year held virtually. 

There is still no sign of neutrinoless beta decay, sterile neutrinos are strongly disfavored (including the RAA, i.e. reactor antineutrino anomaly, which is strongly disfavored), and there is no strong evidence of non-standard neutrino interactions although they aren't ruled out as strongly. The number of active neutrino species determined using W/Z boson decays is exactly three to precision greater than ever previously measured.

Direct limits on the absolute neutrino mass have dropped to 900 meV and promise to drop to 200 meV but are still far weaker than indirect limits. Zero CP violation in neutrino oscillation is ruled out at about two sigma, and the best fit is to near maximal CP violation of -π/2. Measurements of other neutrino oscillation parameters is making slight and inconclusive progress at best.