Out-of-America at the Paleoamerican Odyssey Conference (October 17-19, 2013)
An email from Michael Waters, Director at the Center for the Study of the First Americans at Texas A&M University,
confirms that I’m going to be presenting at the upcoming Paleoamerican Odyssey Conference in Santa Fe, New Mexico. These days, I rarely participate in conferences in either U.S. or Russia, so this is an important occasion for me. Also of note: Alvah (Pardner) Hicks, the long-standing proponent of out-of-America I, will be delivering a poster presentation “Interpreting Archaeological Signatures before Clovis” on Friday, October 18. I can’t wait to see my old friend and his family after a long hiatus.
My own abstract and full presentation with references is below.
The Demographic Isolation of Amerindians and Back Migrations to the Old World in the Late Pleistocene/Early Holocene: From the History of Ideas to Contemporary Scientific Realities
At a time when archaeologists are increasingly seeking to define the pre-Clovis horizon (Dziebel 2000; Waters et al. 2011; Gugliotta 2013), the paper revisits early-to-mid 20th century ideas about human origins in the Americas (Florentino Ameghino) and back migrations from the Americas to the Old World across the Bering Strait (e.g., Franz Boas). Although these speculations have long receded to the fringes of science, the rapid accumulation of paleobiological, genetic, linguistic and ethnological data pertaining to the origins of modern humans in the past 20 years (see Dziebel 2007) asks for the reassessment of the role of the Americas not only as a recipient of modern human populations but also as a source of admixture in the Old World. The discovery of very low genetic diversity among Denisovans – the phenomenon only observed among Amerindians, among living human populations – casts the new light on Pleistocene demographies in Siberia. Mitochondrial DNA furnished evidence for the presence of some Amerindian markers (hgs A2, C1) in Siberia and Northern Europe (DerSarkissian 2011). Autosomal DNA studies (Patterson et al. 2012) have identified “Amerindian admixture” in Western European populations. Americanoid skulls have apparently survived in South Siberia and Central Asia into the Bronze Age (Okunev, Sopka, Chandman/Xiongnu) (Kozintsev et al. 1999; Schurr & Pipes 2011). Coupled with unusually high levels of linguistic diversity in the Americas (Campbell 1997) and some of the most conservative patterns of linguistic structure (Nichols 1992) and kinship organization (Dziebel 2007), this new multidisciplinary data suggests that archaeological research in the Americas and beyond can benefit from a more complex population exchange and isolation model connecting human populations on both sides of the Bering Strait throughout the Late Pleistocene and the early Holocene.
Until just a few years ago, the science of human origins and dispersals seemed to have achieved the unprecedented clarity and simplicity regarding the origin of modern humans and the basic Pleistocene dispersals that led to the formation of present-day continental human populations. The Recent Out-of-Africa-Replacement-with-a-Serial-Founder Effect Model commanded support from archaeology, paleobiology and population genetics to show that modern humans originated in Africa some 200,000 years ago, dispersed out of Africa around 50,000 years ago and reached the New World by 12,000 years. In the course of this blitzkrieg modern humans replaced all pre-existing hominin populations including Neandertals in Europe and West Asia and Homo erectus in both East Asia and Africa.
But in 2010 the world began to change. The improvement of ancient DNA sequencing practices and the availability of ancient and modern full genomes led to the discovery of Neandertal admixture in modern humans both in Africa and outside of it, admixture into modern humans from a previously-unknown hominin species now called Denisovans as well as admixture of both pre-modern African hominins and Eurasian humans into modern African populations including the most isolated Pygmy and Khoisan groups. Modern human morphology was reported at 100,000 years from China (Zhirendong chin) thwarting the 50,000 YBP-like dates for the founding dispersal of humans out of Africa, while behavioral modernity (as expressed in such traits as the use of bone technology, blade production, use of feathers and ochre as ornaments) once thought to have uniquely invented by anatomically modern humans either during the Middle Stone Age in Africa or on the way from Africa to Europe was now shown to have been present among European Neandertals at comparable time depths.
A straightforward serial bottleneck model of human evolution and dispersals yielded to a more complex picture of Pleistocene genetic admixture between ancient hominins and modern humans, behavioral and potentially anatomical convergence between the various hominin groups as well as Neolithic admixture between human continental and subcontinental populations.
The “peopling of the Americas,” too, has grown to become an increasingly complex problem. In addition to the puzzling presence of modern humans at Monte Verde in Chile at 12,500 YBP, the presence of a West Asian mtDNA X lineage in North America and the surprising diversity of New World languages, it has become clear that the earliest Paleoindian culture in the New World, namely Clovis, likely originated not in Alaska but in such southern provinces of North America as Texas (see the Buttermilk Complex; Waters et al. 2011a), that it competed with other technological complexes of similar antiquity such as the Western Stem Point tradition and that megafauna was hunted by humans using bone (and not lithic) technology almost 1000 years prior to Clovis (see the Manis site, Washington; Waters et al. 2011b). Claims for greater than you thought antiquity of man in the New World (e.g., Toca de Tira Peia at 22,000 YBP in Brazil) are now supported by robust dating methods (Lahaye et al. 2013).
The range of potentially fruitful models for ancient human dispersals in the Old World and the New World has dramatically increased in the past decade. Depending on the genetic system in question, modern humans originated in South Africa, East Africa, Central and even West Africa and dispersed between 100,000 and 50,000 years ago using coastal or land route or both with an Arabian standstill or without it. Depending on the kind of evidence scholars look at, they may postulate a single migration to the New World, a dual-, triple- or multiple-migration scenarios mapped onto coastal or interior geographies, with or without a Beringian standstill originating in West Asia, Western Europe, Southeast Asia, South Siberia, the Amur Basin or Chukotka and occurring at 40,000, 20,000 or 15,000 years ago.
What is strangely missing from this cornucopia of models representing nearly every single logical possibility is an overview of evidence supporting the opposite kind of population movement, namely out of America into the Old World. Only a particularly thorough dig into the deepest and most remote strata of the history of ideas would yield an early contention by a founding father of American democracy, Thomas Jefferson (1743-1826) that, considering the remarkable diversity of Amerindian tongues, Amerindians must have been present in America longer than Asians in Asia. At the end of the 19th century, Argentinian paleontologist Florentino Ameghino (1854-1911) postulated the origin of modern humans from New World primates. Finally, in the early 20th century, on the heels of the Jesup North-Pacific Expedition, Franz Boas spoke about a back-migration of Amerindians at the end of the most recent Ice Age that brought the so-called Paleoasiatic peoples (Chukchees, Koryaks, Itelmens, Nivkhs and others) to Siberia.
Although these speculations have long receded to the fringes of science, it’s worth pointing out that Jefferson, Ameghino and Boas were no crackpots. A foremost rationalist and promulgator of Enlightenment, Jefferson was one of the first philologists to begin collecting specimens of American Indian languages in an effort to bring order to the baffling diversity and apparent exoticism of American Indian languages. Two decades later linguists continue to affirm the unique level of linguistic diversity in the Americas on a global scale (Campbell 1997). With language being a defining feature of behavioral modernity, 140-150 language stocks attested in the New World match the level of linguistic fragmentation observed in the Sahul (with the archaeological record for modern humans going back to 60-40,000 years there) and by far exceed the diversity of languages observed in Africa and Europe. And it’s precisely in the areas with highest linguistic diversity that typological linguists find the greatest grammatical trait conservatism. In the words of Johanna Nichols (1992, 281),
“Thus our closest perspective on human language comes from the Pacific and the New World, areas relatively unaffected by the vast spreads in the Old World. The population profile of statistical propensities and diversity of these regions can justifiably be regarded as primordial, and the populations that most clearly show that profile….are our best models of human language.”
Florentino Ameghino was a consummate vertebrate paleontologist and taxonomist. The Paleobiology Database still lists 320 genus names introduced by Ameghino (Novoa & Levine 2010, 100). While his out-of-America ideas were discredited by Ales Hrdlicka in the early decades of the 20th century, only in the past several years the actual human remains that Ameghino used as evidence for extreme antiquity of modern humans in the Argentine Pampas were properly dated and showed terminal Pleistocene to mid-Holocene provenance. This means that for nearly a century Hrdlicka’s verdict regarding the recent origin of Ameghino’s Plio-Pleistocene remains was a mere speculation (Politis et al. 2011). And Ameghino’s intuition may not have been completely off the mark considering that New World primates share with modern humans a whole host of behaviors (such as cooperative breeding, paternal care, pair-bonding as well as elements of articulate speech and even duet singing), which are critical to the evolution of genus Homo and which are thoroughly missing among African apes (see, e.g., Fernandez-Duque et al. 2009; Snowdon 1997).
Finally, Franz Boas was the most meticulous collector of native languages, fish recipes and myths and the most sober theorist of tribal prehistory. As such he was the last person to entertain frivolous ideas. Nevertheless, the intrusive nature of Paleoasiatic languages and myths in Northeast Asia compelled him to identify a back-migration out-of-America as a distinct possibility. Interestingly, the hypothesis of a back-migration of a subset of the New World population into Asia entertained by Jefferson and Boas was based on “cultural” evidence, namely languages and folklore motifs. While typically overlooked as a source of information about ancient population migrations and contacts by the students of archaeology and genetics, this “cultural” evidence nevertheless shows surprising resilience oftentimes exhibiting patterns of unique trait sharing across vast distances (e.g., between Papua New Guinea, Sub-Saharan Africa and Amazonia) – sharing for which specific archaeological and genetic correlates may have gone missing.
In the case of this relatively recent Boasian back-migration, there is mounting genetic evidence that specific Amerindian markers such as mitochondrial A2 and C1 haplotypes are indeed found in Siberia, both Eastern and Western. The principal Amerindian Y-DNA lineage Q1a3a1c is found in the Altai Mountains but with dramatically lower diversity values, again suggestive of a reverse migration. Physical anthropologists have described “Americanoid” skulls at South Siberian sites Okunev and Sopka and Central Asian sites (Chandman/Hunnu), all with Bronze Age dates (Kozintsev et al. 1999; Schurr & Pipes 2011). As Schurr & Pipes write,
“…Western and Japanese scholars have also analyzed craniofacial metric traits in world populations (Fig. 7.3). They observed that the Mongolian Bronze Age Chandman and Mongol Hunnu (Xiongnu) appeared similar to modern Native Americans from the Great Lakes regions, as well as prehistoric Archaic Period individuals from North America (Brace et al 2001; Seguchi 2004).”
As a parallel to this evidence from craniology, ancient DNA samples of Hunnu from Barköl, Xinjiang, China, turned up Y-DNA Q-M3 haplogroup (Kang et al. 2013), and Q-M3 is mostly found in Ket (Yeniseian) and Amerindian peoples, which is also consistent with Edward Vajda’s Dene-Yeniseian linguistic hypothesis.
It is further noteworthy that, according to physical anthropologist Peter Brown, skulls with “Mongoloid” morphology – themselves not the earliest Paleoindian skulls, as we now know thanks to the research by Neves, Pucciarelli, Hubbe, Powell and others – have earlier dates in the New World and not in Asia. Consequently, Brown (1999, 120) was compelled to ask a Boasian question:
“At present the earliest people with a generalised East Asian cranial morphology are probably found in the Americas. Is it a possibility that migration across the Bearing Straits went in two directions and the first morphological Mongoloids evolved in the Americas?”
Considering the relatively recent, ostensibly intrusive and northerly nature of the “Mongoloid” phenotype in Asia, its origin from a Beringian or American source cannot be excluded.
Ancient DNA and whole-genome sequencing have taken the possibility of a New World contribution to the Old World gene pool to another level. In 2012, the team of geneticists and computational biologists led by Nick Patterson (Patterson et al. 2012) reported the presence of “Amerindian-like admixture” in Western European populations. And, correspondingly, predominantly Amerindian C1 lineage of the mitochondria popped up not just among the modern populations of the Amur River Basin in Eastern Siberia but also in Mesolithic samples from Yuzhnyi Olenii Ostrov in northern Russia (Karelia) (Der Sarkissian 2011) as well as in modern populations from Iceland.
Barring some wayward trans-Atlantic contacts in the case of Iceland, the most reasonable explanation for this unexpected distribution of genetic markers is the residual, refugial nature of Amerindian populations with respect to not just Siberia but Eurasia as a whole. This is consistent with Hubbe et al. (2011)’s interpretation of Amerindian craniological material as indicative of the fact that the differentiation of Amerindians into a separate continental population happened prior to the emergence of both Mongoloid and Caucasoid groups.
While the low genetic diversity of Amerindian populations has made Amerindians the perfect antipode to Africans and the “peopling of the Americas” a model example of a well-documented colonization event secure enough to suggest a calibration point for molecular dating techniques applied to other regions, the paucity of archaeological signatures prior to 12,000 years and low genetic diversity may be consistent with not only a late colonization scenario but also with a particular system of ecological adaptation of an ancient, mid-Pleistocene relic. Notably, geneticists sometimes use Amerindian populations not as a model of recent colonization but as a model of archaic demographic structure. According to Lev Zhivotovsky (2001, 704–705), South American Indians is “a reference for microsatellite variation in an ancient African ancestor because their population size is low and might be compared with that estimated for an African ancestor.” As social anthropologists have consistently argued for decades, during their evolution human populations have experienced a relaxation of selective constraints on mating. Originally small and heavily structured populations bound by consanguineal bilateral cross-cousin marriages expanded and developed more panmictic mating behaviors. New World populations furnish some of the best examples of the earliest mating practices, while West Eurasian and African populations have experienced fundamental changes in mating practices (see Dziebel 2007).
Notably, the whole genome sequencing of the South Siberian Denisovan hominin who apparently left genetic traces in modern human populations (Melanesians, out of all groups!) elucidated the extremely low genetic diversity of the Denisovan population. Among the modern human populations South American Karitiana furnished the closest parallel. Correspondingly, Denisovans’ physical reality has eluded archaeologists for decades. Represented only by a pinkie and two molars, the Denisovan population would have been impossible to detect without ancient DNA testing. The Denisovan individual provides a good cautionary tale addressed at those archaeologists who tend to interpret the absence of evidence of human habitation prior to 12,000 years as evidence of absence of modern humans in the Americas. In a similar fashion, an extensive ancient DNA study suggests that around 60,000 years ago there took place a major colonization of the Eurasian landmass by woolly mammoths originating in the New World (Palkopoulou et al. 2013) – something that paleontology has never been able to document. If mammoths spread across the Eurasian landmass from an American source, it would not be hard to imagine human hunters following in their footsteps. From this angle, the surprising discovery of the most basal B0006 lineage on human X chromosome at highest frequencies in the Americas (see Zietkiewicz et al. 2006) parallels the basal position of North American Clade I in the mammoth phylogeny.
The current stage in human origins research is characterized by data explosion and the enrichment of the traditional archaeological and paleobiological perspectives with the perspectives derived from the large databases of linguistic, ethnological and population genetic traits. It is therefore important to keep an open mind for both classic and novel – even seemingly preposterous – models of human evolution and dispersals. Ultimately, a thorough, well-balanced and fully four-field anthropological approach will prevail over more parochial, single-discipline, ad hoc theories of how a particular part of the world was peopled. This approach will undoubtedly result in the inclusion of New World monkeys and humans into the complete story of primate and human physical and behavioral evolution characterized by forces of convergence, common descent and admixture.
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