The Ice-Free Corridor and the Early Peopling of the Americas

Some archaeological sites across the length and breadth of the Americas point to an early peopling of the continent. The key questions are:

When?

and

By what route?

By looking at a map, there are basically there are 5 routes:

Route 1:

The Solutrean hypothesis: claims that the earliest human migration to the Americas took place from Europe, during the Last Glacial Maximum, via North Atlantic pack ice. According to this hypothesis, people of the Solutrean culture, from the Atlantic seaboard, of Europe migrated to North America by boat between 21,000 to 17,000 years ago. They brought their methods of making stone tools with them and provided the basis for the later (c. 13,000 years ago) Clovis technology. Originally proposed in the 1970s, it was brought to prominence by Dennis Stanford and Bruce Bradley (2012), in their book Across Atlantic Ice.

Evidence for: superficial similarity of stone tools from the two regions, the European (Solutrean) preceding the American (Clovis).

Evidence against: Mitochondrial haplogroups of the Americas, show absolutely no mtDNA from European sources commensurate with the timeframe suggested. Theory, therefore, generally, rejected.

Route 2:

Pre-Columbian migration or exploration from Africa. Niede Guidon, the Brazilian archaeologist has been quoted as saying, she believed that"... humans … might have come not overland, from Asia but by boat from Africa", with the journey taking place 100,000 years ago.

Secondly, José Melgar, discovered the first colossal head made by the Olmec culture at Tres Zapotes in 1862. Ivan Van Sertima, later, suggested that the features of the heads were distinctly African and hence, that contact between the African continent and central/south America had taken place. The Olmec culture existed from approximately 1200 BCE to 400 BCE. Consequently, these heads, if they were genuinely, made by African migrants, are far more recent than the accepted dates for the peopling of the Americas.

Leo Wiener, also suggests some religious, symbolic and linguistic similarities between certain Arabian cultures and those of Mesoamerica. These claims have come in for a great deal of academic criticism, and again lie outside the timeframe of the initial peopling of the Americas.

Evidence for: vague similarities between Olmec statuary and African phenotypes.

Evidence against: the absence of genetic evidence in modern populations from the Americas. Particularly the lack of older mtDNA macrohaplogroups such as L. However, the transport of slaves from west Africa beginning in the 15^th century and their genetic legacy, may obscure any older signal of an early African colonisation. Theory, therefore, generally, rejected.

Route 3:

Across the Pacific as an extension of the Polynesian colonisation of the south-sea islands. Evidence of trans-Pacific contact from Polynesia to south America, is actually, quite, strong. The sweet potato, Ipomoea batatas, which is native to the Americas, was widespread in Polynesia when Europeans first reached the Pacific. Current academic opinion, is that it was brought to eastern Polynesia, from south America, and spread across wider, Polynesia from there. It has been suggested that it was brought by Polynesians who had travelled to South America and back, or that South Americans brought it to the Pacific. The problem is that the dates don’t fit. Sweet potato has been radiocarbon-dated in the Cook Islands to 1000 CE and its probable first introduction to Polynesia was around ca. 700 CE. Additionally, it is possible that the plant could successfully float across the ocean if discarded from the cargo of a boat.

Other evidence, has been put forward, that some, chicken races from south America also have Polynesian mtDNA strains, although the evidence is disputed.

Stronger evidence of Polynesian migration to the Americas, comes from genetic research carried out in the last decade. According to Gonçalves et al. (2013), some members of the now extinct Botocudo people, who lived in the interior of Brazil, were found to have been members of mtDNA haplogroup B4a1a1, which is normally found only among Polynesians and other subgroups of Austronesians. This was based on an analysis of fourteen skulls. Two belonged to B4a1a1 (while twelve belonged to subclades of mtDNA Haplogroup C1 common among Native Americans). The research team examined various scenarios, including prehistoric migration, from Polynesia, 19^th century slave trade from Polynesia to Peru and 19^th century slave trade from East Africa including Madagascar. As mtDNA haplogroup B4a1a1 occurs in all these areas, any could plausibly be a potential source. However, the emergence of this haplogroup has been estimated to between 8300BP and 9300BP and consequently it is rather too late

Evidence for: various plant and animal introductions showing two-way contact between Polynesia and South America.

Evidence against: the absence of widespread, Polynesian mtDNA haplogroups in modern populations from the Americas.

Routes 4 and 5:

I have posted extensively on the peopling of the Americas via the Bering Land Bridge (here, here and here). For reasons laid out in those posts, the vast, majority, of academics and I, believe that the Americas were populated via Beringia, either along the coast (route 4), or via the interior of Alaska; Canada and finally the north-western states of the USA by a route known as the Ice-Free Corridor (route 5).

The question of the origins of Native Americans had perplexed scientists for many decades. So, what evidence would need to be found to confirm the migration of people from north east Asia to the Americas via Beringia?

Broadly, if the mitochondrial DNA and y-DNA of both populations was found to the same, in the relevant time-period, and no other sources of genetic ancestry could be found, it would be case proved. Therefore, Native Americans were some of the first people to have their genetic inheritance studied and categorised.

DNA evidence supporting a Beringian entry into the Americas

Mitochondrial DNA linages.

Initial work on Native American DNA began back in the late 1980’s and early 1990’s.

Soon, through the work of Schurr et al. (1990); Torroni et al. (1993); Neel et al. (1994); Merriwether et al (1995); Pena, et al (1995) and Santos et al. (1995), it became apparent, that most Native American haplotypes fell within certain haplogroups.

As Schurr (2000) comments: “Over the past 10 years, however, new methodologies have provided a, number of, important insights into the peopling of the New World.

Molecular genetic studies of the variation of mitochondrial DNA (mtDNA) in Siberian and Amerindian populations have allowed further inferences to be made about the timing of the colonisations, the number of migrations that reached the New World, and possible regions from which ancestral Native Americans might have originated. Most notably, the new mtDNA data suggest not only a very early movement of peoples into the New World but also the genetic contributions of populations originating outside of Siberia, from other parts of Asia. Overall, the mtDNA research implies that the colonization of Siberia and the Americas was more complex than previously supposed—that there were, in fact, multiple expansions of ancient peoples that contributed to the genetic diversity in aboriginal Siberian and Amerindian populations.”

The current consensus (with some caveats) is that, all indigenous extant, Amerindian mtDNA can be traced back to five haplogroups, A, B, C, D (Schurr et al. 1990; Achilli et al. 2008) and X (Malhi and Smith 2002; Reidla et al. 2003).

Moreover, the links between these haplogroups and north east Asian/Siberian populations was clearly demonstrated by comparative studies – see Starikovskaya et al. (2005), for example.

However, there have been some surprising results from ancient skeletal material, reported.  Malhi et al. (2007) found, two samples with mtDNA haplogroup M. As the authors say: “As both China Lake samples were determined to lack the markers definitive of haplogroups A, B, C, or D, they were subsequently screened for the AluI site gain at np 10397, definitive of macro-haplogroup M,..”. It was possible, for the authors, to use this approach because an AluI site gain at np 10397 is produced by a C-to-T transition at np 10400 – one of the defining SNPs for haplogroup M.

When the authors detected the mutation for the M haplogroup, they decided to take the results at face value and try to characterise the M haplotype they had apparently found, focusing on those from the other side of the Beringian land bridge.

This was extremely unusual. Almost all studies report such results as ‘other haplogroup’ without going into details. Instead Malhi et al. (2007), made new primers to check whether their potential M samples were from certain north east Asian haplogroups, but none of the downstream markers for the expected haplogroups, namely M7, M8 or M9, were found. Looking at the distribution of these haplogroups, one can see why Malhi et al. (2007), chose to look for them. All are found within the south central or east Siberian region or coastal far north east Asia. In particular, certain, ethnic groups close to Beringia host subclades of these haplogroups. For example, the Udegey, Koryaks, Itelmens, Chukchis, Tuvans, Altayans and Khakassians.

An Udege family. Udege are a people who live in the Primorsky Krai and Khabarovsk Krai regions, on the coast, near the Kamchatka peninsula, in Russia. From Wikipedia Commons (2018).

Disappointingly, Malhi et al. (2007) failed to find any of the mutations needed to pinpoint the haplogroup: “Both China Lake individuals belong to haplogroup M, exhibiting the AluI site gain at np 10397. They do not, however, belong to haplogroup C, D, or sub-haplogroup M7, M8, or M9, all representing derived forms of haplogroup M. The individuals likely do not belong to haplogroup G as they lack HVRI mutations specific to its sub-clades. Both individuals exhibited identical HVRI sequences.”

What then are we to make of this? Well as the SNPs for everything downstream of M7 are absent, the mtDNA must belong to one of the more basal haplogroups M*, M1, M2, M3, M4, M5 or M6.

Kemp and Schurr (2010) commenting that paper say “two individuals from the China Lake site in the British Columbia interior were determined to belong to a form of haplogroup M that has yet to be identified in any extant Native American population. As these individuals, both exhibited a very rare supratrochlear spur on their left humeri, it was believed by the physical anthropologists who examined the remains that these males were full siblings and possibly twins. This haplotype possibly represents a sixth founding haplogroup, one that may have gone extinct in the last 5,000 years or so. However, further analysis of this mtDNA is required to rule out prehistoric gene flow from the Beringian region, where haplogroups M derived lineages not seen in the Americas are common. Given the profound effect that genetic drift has had on the Native American gene pool, this haplotype may still exist in unstudied populations.”

Additionally, a little known sample with haplotype M has been discovered in South America. From Carpenter et al. (2013): “The three Peruvian mummies fell into haplogroups B2, M (an ancestor of D), and D1, all derived from founder Native American lineages and previously observed in both pre-Columbian and modern populations from Peru.”

Chachapoya sarcophagi containing the mummies. Picture credit: ABC news (2015).

Genetiker (2014), comments on the Peruvian mummy: “The calls for NA40 are strange. The published haplogroup for NA40 was M, and NA40 had 1 of 2 mutations for M and 5 of 5 mutations for M8, but NA40 also had 4 of 4 mutations for N, and 1 of 1 mutation for R.” Whilst this blog is run by an amateur, with unknown qualifications in genetics, by checking the SNP numbers he cites for the Chachapoya, NA40 mummy (namely: M-G15043A; M8-A4715G; M8-C7196a; M8-G8584A; M8-A15487t; M8-T16298C; N-G8701A; N-C9540T; N-G10398A; N-C10873T; R-T12705C) against the PhyloTree Build 17, from phylotree.org (2016), we can see he is entirely correct, except that NA40, now has 1 of 4 mutations for haplogroup M. I assume this is due to the defining mutations having changed from the build that Genetiker used in 2014.

So, what are we to make of these results? Are some of the mutations misreported? Has there been contamination of the sample? Is the M haplogroup an unknown one due to genetic drift producing private mutations? Or could this be one of those rare cases of where mtDNA has been passed on from both mother and father? Taken as a whole these mt-SNP calls, most likely indicate that the mummy is mitochondrial haplogroup M8, as the sample contains all the mutations required for this assignment. Furthermore, this haplogroup, is one of those, that might have been expected to cross the Bering Strait, from one of the populations mentioned above. Especially if an early migration, say pre-20,000BP, is considered.

Furthermore, Lalueza et al. (1997), found a mtDNA sample of haplogroup N in Ancient DNA from bones and teeth of 60 individuals from four extinct human populations from Tierra del Fuego-Patagonia As they say of the Selknam: “Haplotype N includes the single haplotype not segregating into any of the four major Amerindian haplogroups.” Whether this was due to the haplotype being unrecognised as X, or whether it truly belonged to basal N haplotype, I have been unable to ascertain.

It therefore seems likely that some ancient, genetic diversity, previously extant in the Americas may have been lost due, most likely to, the massive, native, population reduction seen post European colonisation.

y-DNA haplogroups

Research on y-DNA in Native Americans, followed a little later due to technological barriers. However, it followed much the same pattern, with the y-DNA of Native Americans found to be from two main haplogroups: Q and C. Additionally, links were also proved with north east Asian and/or Siberian haplogroups – see Santos et al. (1999); Battaglia et al. (2013).

The current state of knowledge regarding Native American y-DNA haplogroups was summarised by Kemp and Schurr (2010) “Currently, only Y chromosome haplogroups C and Q are believed to be indigenous to the Americas, with other haplogroups most likely being the product of post contact admixture (Bolnick et al. 2006; Malhi et al. 2008; Zegura et al. 2004). However, Lell and colleagues (2002) and Bortolini and colleagues (2003) have suggested that certain R1-M173 haplotypes may also have been brought to the Americas by the proto–Native American migrants. R1-M173 haplotypes appear at low frequencies in only indigenous populations of North and Central America, including the Athapaskan-speaking Chipewyans (Bortolini et al. 2003; Lell et al. 2002). Although quite diverse in eastern Siberia, there is some debate as to whether those seen in Native Americans are indigenous in origin, owing to their also being commonly observed in European populations (Lell et al. 2002; Tarazona-Santos and Santos 2002).

This is an intriguing, but controversial aspect of y-DNA haplogroups amongst Native Americans. Controversial because most clades of y-DNA haplogroup R, are, European in origin. Therefore, some less than scrupulous groups within America could use this evidence to promulgate, a white supremacist agenda, about the peopling of the Americas. Consequently, since these papers, very little research has been brought forward, concerning y-DNA haplogroup R within the Americas. Put simply, the subject is avoided by academics, as it is too politically charged. An in depth, and persuasive review of these papers was written up by Austin Whittall over at the Patagonian Monsters blog (see here).

Some of the points he makes are very cogent. However, without further research the possibility of y-DNA haplogroup R having some Native American subclades is an open question. In my opinion, we need to find evidence in the form of extant or fossil DNA of the form R* or of R clades with unique mutations not found in Europe, to be certain that some form of y-DNA R is Native to the Americas and not entirely due to European admixture.

Autosomal DNA

Recently, researchers in paleogenetics have made some key discoveries. Not of further, previously undetected mtDNA or y-DNA lineages but by looking at autosomal DNA.

I won’t go into every paper here, however Raghavan et al. (2013) have looked at an ancient sample from central Asia:

“Here we sequence the draft genome of an approximately 24,000-year-old individual (MA-1), from Mal’ta in south-central Siberia, to an average depth of 1X.”

Mock-up of the Mal’ta boy burial. From Kelly Graf via Nature News (2013).  Original caption reads: The remains of a boy from Palaeolithic Siberia — shown here in a burial reconstruction at the Hermitage Museum in St. Petersburg.

“The MA-1 mitochondrial genome belongs to (an undifferentiated branch) of haplogroup U, which has also been found at high frequency among Upper Palaeolithic and Mesolithic European hunter-gatherers, and the Y chromosome of MA-1 is basal to modern-day western Eurasians and near the root of most Native American lineages (in fact basal R*). Similarly, we find autosomal evidence that MA-1 is basal to modern-day western Eurasians and genetically closely related to modern-day Native Americans, with no close affinity to east Asians. This suggests that populations related to contemporary western Eurasians had a more north-easterly distribution 24,000 years ago than commonly thought.

Furthermore, we estimate that 14 to 38% of Native American ancestry may originate through gene flow from this ancient population. This is likely to have occurred after the divergence of Native American ancestors from east Asian ancestors, but before the diversification of Native American populations in the New World. Our findings reveal that western Eurasian genetic signatures in modern-day Native Americans derive not only from post Columbian admixture, as commonly thought, but also from a mixed ancestry of the First Americans.”

Sequencing of a second specimen from the region, Afontova Gora 2 (AG2), revealed a close similarity in the autosomal DNA of the two specimens. Unlike Mal’ta (MA1) however AG2 had, yDNA Q1a1. The mtDNA was not disclosed. Autosomally they were very similar, the allele frequencies showing the two specimens were from very closely related populations.

A second important ancient specimen from Asia, namely the 40,000-year-old, Tianyuan individual from near Beijing, had its DNA successfully sequenced by Yang et al. (2017).

Tianyuan Man skeleton. Source unknown.

The authors comment: “We also find that ancient and present-day East and Southeast Asians and Native Americans are all more closely related to each other than they are to the Tianyuan individual. We also find that the Tianyuan individual shares more alleles with some Native American groups in South America than with Native Americans elsewhere.

Most Asian and Native American populations share similar numbers of alleles with the Tianyuan individual. However, three South American populations—the Surui and Karitiana in Brazil (‘‘Amazonians’’) and the Chane in northern Argentina and southern Bolivia—share more alleles with the Tianyuan individual than other Native American populations do. The two Amazonian populations were recently shown to share more alleles with the present-day Papuan and Andamanese Onge than with other Native Americans, suggesting that at least two populations contributed ancestry to Native Americans in Central and South America. A 12,000-year-old individual from North America (Anzick-1) does not share more alleles with the Tianyuan individual (or with Oceanians or the Andamanese) than with other Native Americans. The Surui and Chane show the highest levels of allele sharing with the Tianyuan individual (Dstat: Surui/Chane, Mixe, Tianyuan, Mbuti), which is higher than, or similar to, levels of allele sharing with the Papuan or Onge. Using an analysis robust to uncertainty of the exact population history, we find that the Amazonians can be described as a mixture of other Native American populations and 9%–15% of an ancestral population related to the Tianyuan individual, the Papuan, or the Onge (SE 4%–10%). Although the SE is high, we note that the Amazonians are consistently modelled as a mixture of other Native Americans and the Tianyuan individual, the Papuan, or the Onge. The mixture proportion estimates are also similar across all analyses, indicating that the relationship between the Tianyuan individual and the Amazonians is similar to, that reported between the Papuan and the Amazonians and Onge and the Amazonians.

We also studied a model relating the Tianyuan individual to other ancient individuals and present-day populations using a base model including the Altai Neanderthal, Denisovan, Ust’-Ishim, and Kostenki14. We added the Tianyuan individual, Mal’ta1, and the present-day Ami, Mixe, Surui, and Papuan. Because present-day European populations have recent ancestry from an unknown Basal Eurasian population, we use Kostenki14, which has recently been shown to have no Basal Eurasian ancestry to represent Europeans. We caution that our model is unlikely to reflect the true population relationships, as we cannot model many demographic features, such as population structure or continuous migration. Intriguingly, however, within this simple model, we find that all three South American populations can be modelled as sharing ancestry not only with other Native Americans, but also with populations related to the Tianyuan individual and the Papuan.

The fact that the Tianyuan individual, who lived in mainland Asia about 40,000 years ago, has affinities to some South American populations that is as strong as or stronger than that observed for the Papuan and Onge suggests that a population related to the Tianyuan individual, as well as to the present-day Papuan and Onge, was once widespread in eastern Asia. This group or another Asian population related to this group persisted at least until the colonization of the Americas and contributed to the genomes of some Native American populations.”

An important ancient individual, namely Anzick 1, dating to ca. 12,600BP was recently fully sequenced by Rasmussen et al. (2013). 

Anzick 1 cranium, just prior to reburial. Picture credit: White (2015). 

From the paper: “Here we report the genome sequence of a male infant (Anzick-1) recovered from the Anzick burial site in western Montana. The human bones date to 10,705 +/- 635 14C years BP.. and were directly associated with Clovis tools. Initial genetic screening of the Anzick-1 skeletal remains using PCR coupled with cloning and Sanger sequencing yielded a mitochondrial DNA (mtDNA) haplogroup assignment of D4h3a. The D4h3a haplogroup was verified and further characterized in the subsequent shotgun sequencing of Anzick-1. D4h3a is one of the rare mtDNA lineages specific to Native Americans, is distributed along the Pacific coast in North and South America among contemporary populations, and is also present in ancient specimens. Its current distribution has been interpreted as evidence for an early coastal migration route. Our findings of this mtDNA haplogroup inland in the oldest skeleton from the Americas to be mtDNA-typed to date question such interpretation and underscore the view that current distributions of genetic markers are not necessarily indicative of the movement or distribution of peoples in the past. The Anzick-1 D4h3a does not carry any of the polymorphisms that define the several subgroups of the haplogroup and is thus placed at the root of D4h3a. Our finding suggests that the origin of the D4h3a branch is likely to be at the upper bound of the previously obtained estimate of 13,000 +/- 2,600 calendar years BP 14, or possibly even older.”

On the yDNA the authors had this to say: “We determined the Y-chromosome haplogroup to be Q-L54*(xM3) and, along with 15 previously analysed Y-chromosome sequences, we constructed a tree to illustrate the phylogenetic context within haplogroup Q. Confining our analyses to transversion single nucleotide polymorphisms (SNPs), we leveraged the date of Anzick-1 to estimate a divergence time between haplogroups Q-L54*(xM3) and Q-M3, two of the major founding Y-chromosome lineages of the Americas, of approximately 16,900 years ago (95% confidence interval: 13,000–19,700).”

In terms of the autosomal DNA the authors say: “We assessed the genome-wide genetic affinity of the Anzick-1 individual to 143 contemporary non-African human populations by computing outgroup f3-statistics, which are informative on the amount of shared genetic drift between an individual and other populations. The data set included 52 Native American populations, for which genomic segments derived from recent European and African admixture have been excluded. We found that the Anzick-1 individual showed a statistically significant closer affinity to all 52 Native American groups than to any extant Eurasian population. We sequenced the genome to an average depth of 14.43 and show that the gene flow from the Siberian Upper Palaeolithic Mal’ta population into Native American ancestors is also shared by the Anzick-1 individual and thus happened before 12,600 years BP. Our data are compatible with the hypothesis that Anzick-1 belonged to a population directly ancestral to many contemporary Native Americans.

Finally, we find evidence of a deep divergence in Native American populations that predates the Anzick-1 individual.”

This last part concerning the shared autosomal background of all Native Americans with the North East Asian Mal’ta population is regarded as another piece of evidence that conclusively demonstrates that Native Americans migrated from North Eastern Asia

MA-1 is the only known example of yDNA R* (R-M207*) – that is, the only member of haplogroup R* that did not belong to haplogroups R1, R2 or secondary subclades of these. The mitochondrial DNA of MA-1 belonged to an unresolved (presumably very basal) subclade of haplogroup U.

A paper by Skoglund et al. (2015), showed that contemporary Amazonian populations and Australasian groups (Papuans, Australians, and Andaman Islanders) shared some very ancient ancestry.

They dubbed it “Population Y”. Importantly, this ancestry signal is not consistent with a trans-Pacific migration from that region; the signal is very old and very subtle.

From the paper: “These results do not imply that an unmixed population related anciently to Australasians migrated to the Americas. Although this is a formal possibility, an alternative model that we view as more plausible is that the ‘Population Y’ (after Ypykue´ra, which means ‘ancestor’ in the Tupi language family spoken by the Suruı´ a Karitiana) that contributed Australasian-related ancestry to Amazonians was already mixed with a lineage related to First Americans at the time it reached Amazonia. When we model such a scenario, we obtain a fit for models that specify 2–85% of the ancestry of the Suruı´, Karitiana and Xavante as coming from Population Y. These results show that quite a high fraction of Amazonian ancestry today might be derived from Population Y. At the same time, the results constrain the fraction of Amazonian ancestry that comes from an Australasian related population (via Population Y) to a much tighter range of 1–2%.

We have shown that a Population Y that had ancestry from a lineage more closely related to present-day Australasians than to present-day East Asians and Siberians, likely contributed to the DNA of Native Americans from Amazonia and the Central Brazilian Plateau.

This discovery is striking, in light, of interpretations of the morphology of some early Native American skeletons, which some authors have suggested have affinities to Australasian groups. The largest number of skeletons that have been described as having this craniofacial morphology and that date to younger than 10,000 years old have been found in Brazil, the home of the Suruı´, Karitiana and Xavante groups who show the strongest affinity to Australasians in genetic data.

However, in the absence of DNA directly extracted from a skeleton with this morphology, our results are not sufficient to conclude that the Population Y we have reconstructed from the genetic data had this morphology.

An open question is when and how Population Y ancestry reached South America. There are several archaeological sites in the Americas that are contemporary to or earlier than Clovis sites. The fact that the one individual from a Clovis context who has yielded ancient DNA had entirely First American ancestry suggests the possibility that Population Y ancestry may be found in non-Clovis sites. Regardless of the archaeological associations, our results suggest that the genetic ancestry of Native Americans from Central and South America cannot be due to a single pulse of migration south of the Late Pleistocene ice sheets from a homogenous source population, and instead must reflect at least two streams of migration or alternatively a long drawn out period of gene flow from a structured Beringian or Northeast Asian

source. The arrival of Population Y ancestry in the Americas must in any scenario have been ancient: while Population Y shows a distant genetic affinity to Andamanese, Australian and New Guinean populations, it is not particularly closely related to any of them, suggesting that the source of population Y in Eurasia no longer exists; furthermore, we detect no long-range admixture linkage disequilibrium in Amazonians as would be expected if the Population Y migration had occurred within the last few thousand years.”

This last year, has had an explosion of genetics papers from the Americas, with three papers being publish on the subject in under a month.

Moreno Mayar et al. (2018), sequenced genomes from 15 ancient human remains.

These include remains from Trail Creek Cave 2, Alaska (ca. 9 ka); Big Bar Lake, British Columbia (ca. 5.6 ka); and Spirit Cave, Nevada (ca. 10.7 ka); four individuals from Lovelock Cave, Nevada (ranging from 1.95 to 0.6 ka); five individuals from Lagoa Santa, Brazil (ca. 10.4 to ~9.8 ka old); one individual each from the Punta Santa Ana and Ayayema sites in Patagonian Chile (ca. 7.2 and ca. 5.1 ka respectively); and an Incan mummy from Mendoza, Argentina (ca. 0.5 ka old).

“modelling indicates that the Mixe most likely carry gene flow from an unsampled outgroup and form a clade with Lagoa Santa. Including nonzero outgroup admixture into the Mixe when fitting an f statistics–based admixture graph resulted in a significantly better fit (likelihood ratio test; P < 0.05). Hereafter, we refer to that outgroup as unsampled population A (UPopA), which is neither AB, NNA, or SNA and which we infer split off from NAs ~24.7 ka ago, with an age range between 30 and 22 ka ago [95% confidence interval (CI); this large range is a result of the analytical challenge of estimating divergence and admixture times in the absence of UPopA genome data].” They go on to say: “To test for the Australasian genetic signal in NAs, we computed D statistics of the form D(NA, NA; Eurasian, Yoruba), where NA represents all newly sequenced and reference high-depth NA genomes (13). In agreement with previous results (Skoglund 2015), we found that the Amazonian Suruí share a larger proportion of alleles with Australasian groups (represented by Papuans, Australians, and Andaman Islanders) than do the Mixe. Lagoa Santa yielded results similar to those obtained for the Suruí: The analyzed Lagoa Santa genome also shares a larger proportion of alleles with Australasian groups, but not with other Eurasians, than do Mesoamerican groups (the Mixe and Huichol)..”

The words “unsampled outgroup” have caused somewhat of a firestorm in the blogosphere. From Adnaera (2018): “When they say "unsampled", they mean unsampled. So no, we’re not talking about potentially "anyone", but quite specifically about a population that does not only seem to be an outgroup to NA, but also an outgroup to Eurasians.

If this is true, then who can be an outgroup to Eurasians? Basically there are 4 options:

– An African population (meaning a population that went Out of Africa after the main OoA event that gave birth to most Eurasians, and that somehow reached Central America some 9 kya). This one is the least likely, really.

– An early OoA population (meaning a population that went OoA before the main OoA event). We know from archaeology (and with some support from genetics) that such early events did occur but they hardly contributed to later Eurasian populations (maybe a tiny bit to some SE Asian/Australasian populations?). So this one would mean that such population made it to the Americas and survived somewhere around Central America until the second major wave arrived.

– Archaic hominins. Like Neanderthals or Denisovans. A small admixture from such groups (on top of what other NA already have) would make the shared drift of Mixe with all other AMH be lower. So is it possible that some form of archaic hominin lived in America and survived until some 9 kya?

– A fourth option would be an early "generic" Eurasian population, something similar, to Ust-Ishim samples from 45 kya, but not directly related to Ust-Ishim."

Obviously, some of these options are more likely than others, as Antonio states. Some commentators have been particularly attracted by option three: ‘Archaic hominins’. See for instance Whittall (2018).

However, leaving that possibility aside, this unsampled population, could, perhaps represent an even older migration of AMH. A population related to the first out of Africa even ca. 120,000 to 80,000BP, – in other words a population more basal than that which gave rise to the ‘Clovis generation’ if you like. There is, actually, some, evidence for this – see the discussion on migration routes and Tibetan DNA below.

Posth et al. (2018), sequenced genomes from 49 ancient individuals. The authors explain their findings thus: “Most important, our discovery that the Clovis-associated Anzick-1 genome at ca.12,800 BP shares distinctive ancestry with the oldest Chilean, Brazilian, and Belizean individuals supports the hypothesis that an expansion of people who spread

the Clovis culture in North America also affected Central and South America, as expected if the spread of the Fishtail Complex in Central and South America and the Clovis Complex in North America were part of the same phenomenon (direct confirmation would require ancient DNA from a Fishtail-context).

However, the fact that the great majority of ancestry of later South Americans lacks specific affinity to Anzick-1 rules out the hypothesis of a homogeneous founding population. Thus, if Clovis-related expansions were responsible for the peopling of South America, it must have been a complex scenario involving arrival in the Americas of sub-structured lineages with and without specific Anzick-1 affinity, with the one with Anzick-1 affinity making a minimal long-term contribution. While we cannot at present

Determine when the non-Anzick-1 associated lineages first arrived in South America, we can place an upper bound on the date of the spread to South America of all the lineages represented in our sampled ancient genomes as all are ANC-A and thus must have diversified after the ANC-A/ANC-B split estimated to have occurred ca. 17,500–14,600 BP.”

What Posth et al. (2018) did not find was ancestral signal related to Australasian groups (Papuans, Australians, and Andaman Islanders), as Skoglund (2015) and Moreno-Mayar et al (2018) had done. This is unsurprising really, as the populations sampled by Posth et al. (2018) were not those in which ancient Australasian signal had been found by Moreno-Mayar et (2018) and Skoglund (2015).

The third paper to come out in the same month was by Lindo et al. (2018). These authors sequenced the genomes of seven Andean highlanders from lake Titicaca, Peru. They compared them to two modern, highland and lowland populations from nearby regions, namely the Aymara of highland Bolivia and the Huilliche-Pehuenche of coastal lowland Chile. The samples spanned a date range of 6800 to 1400 calendar years BP. Considering their small sample size, and relatively recent dates, their results were, understandably, not Earth-shattering. From the authors: “Both the Rio Uncallane and K1 trace their genetic ancestry to a single component, which is also shared by the modern Andean populations of the Quechua and the Aymara. SMP5 not only traces most of this ancestry to the same component but also exhibits a component found in Siberian populations, specifically the Yakut. USR1, a 12,000-year-old individual from Alaska hypothesized to be part of the ancestral population related to all South American populations, also shares this component, as do previously published ancient individuals from North America (i.e., Anzick-1, Saqqaq, and Kennewick).”

Furthermore, they add the following interesting comment: “Although our samples do not extend beyond 7000 years BP, we were, able to model the initial entry into the Andes after the split between North and South American groups. Our model, using a

mutation rate of 1.25 × 10⁻⁸, shows a correlation with archaeological evidence regarding the split between North and South groups occurring nearly 14,750 years ago (95% CI, 14,225 to 15,775), which agrees with the oldest known site in South America of Monte Verde in southern Chile (~14,000 years BP).” I find the use of that mutation rate somewhat suspect. Given that some authors have suggested a much lower mutation rate, this would put the North American and South American populations back in time considerably, which would, in fact, fit far better with the correct dates for Monte Verde (see here).

The authors also examined the sequences of the Andean Highlanders for adaptation to altitude. One might have hoped that they would find genes, similar, to, EPAS1 or EGLN1 that give Sherpas and Tibetans resistance to hypoxia, given that Native Americans have autosomal links to central and east Asian populations. They did not.

Lastly Wong et al. (2019) confirm the links between Native Americans and the peoples of north east Asia: “A particularly surprising finding was the genetic link between 24,000-yr-old Siberian Mal’ta boy, Native Americans, and the Western Siberians Mansi, Khanty, and Nenets. This finding demonstrates a strong genetic link between Western Siberians and Native Americans due to their common ANE ancestry… Native Americans trace 42% of their ancestry to ANE and 58% to a common ancestor of Eastern Siberians and East Asians.”

Insights from the DNA papers

So, what insights have we gained into the peopling of the Americas by studying this plethora of papers?

Taking the papers one at a time we can say, with some degree of confidence that:

1. Pre-Malhi (2007): America populated initially via Beringia by peoples from eastern Siberia/Asia. Mitochondrial haplogroups limited to A, B, C, D and X, with y-DNA limited to haplogroups Q and C. However, while this is the currently, academically accepted theory, some research conducted in the early 2000’s suggested that some clades of R1-M173 haplotypes may be of, Native, American origin, this however has not been fully investigated.

2. Malhi et al. (2007) and Carpenter et al. (2013) find haplogroup M in America. The second set of author’s data show that the haplotype was some form of M8, also found in populations from eastern Siberia.

3. The Mal’ta boy genome showed that the Y chromosome of MA-1 is basal to modern-day western Eurasians and near the root of most Native American lineages (in fact basal R*). Similarly, we find autosomal evidence that MA-1 is basal to modern-day western Eurasians and genetically closely related to modern-day Native Americans, with no close affinity to east Asians. In other words the population ancestral to both MA1 and Native Americans regarded as Western Eurasian, had a much more north eastern distribution prior to 25,000BP and contributed to both subsequent populations.

4. Rasmussen (2013), showed that Anzick-1 individual had a statistically significant closer affinity to all 52 Native American groups than to any extant Eurasian population. They also, showed that the gene flow from the Siberian Upper Palaeolithic Mal’ta population into Native American ancestors is also shared by the Anzick-1 individual and thus happened before 12,600 years BP. Interestingly Anzick1’s mtDNA was basal D4h3a, that is without any of the subsequent mutations found in other samples of this haplotype. These later samples are generally spread down the Pacific coastline of both north and south America, and hence had been used as evidence for a coastal migration route for the first peopling of the Americas. The fact that Anzick1 is early and inland (the wrong side of the Rockies), is a point against this hypothesis and in fact may indicate an, early Ice-Free Corridor entry into the Americas.

5. Skoglund (2015) found a genetic signal from ‘Population Y’, contributed Australasian-related ancestry to Amazonian tribes and peoples of the central Brazilian plateau, such as Suruı´, Karitiana and Xavante was already mixed with a lineage related to First Americans at the time it reached Amazonia. This was the first clear signal of a, possibly earlier migration into the Americas.

6. Insights gained by Yang et al. (2017), from the study of the Tianyuan man’s autosomal DNA show that Native American populations share similar numbers of alleles with the Tianyuan individual. However, three South American populations—the Amazonian Surui and Karitiana in Brazil and the Chane in northern Argentina and southern Bolivia—share more alleles with the Tianyuan individual than other Native American populations do. Again, this finding shows that an earlier wave of migration may have occurred before the main wave (ca. 16,000BP). This wave may have entered the Americas some time, around 40,000BP or possibly earlier.

7. Moreno-Mayar et al. (2018), confirm that some Amazonian populations harbour a genetic contribution from an ‘unsampled outgroup’. Whether this represents a contribution from archaic hominins (in my opinion unlikely), or an older migration of AMH before the last glacial maximum, is yet to be firmly established.

Migration to the Americas, starting early - implications

One of the main preoccupations of this blog, is unashamedly "When were the Americas first peopled?". Archaeological evidence points to a period well before the Clovis era, with moderately good evidence of a first arrival of anatomically modern humans reaching the continent ca. 50,000BP.

In the context of this blog post, substantiating evidence would have to be found amongst the DNA of Native Americans. Above I have shown that there is indeed now, some evidence of this hypothesis.

However, an early entry must presumably have included more basal haplogroups to those now agreed as unequivocally Native American. As the agreed haplogroups are A, B, C, D and X, this would mean that the progenitors of these haplogroups – M in the case of C and D, and N with respect to   A, B and X would have to be in the right place, at the right time to cross the Bering Strait and enter the Americas early.

The right place would be north western Siberia. The right time would be prior to 50,000BP. What evidence do we have for this?

Well there are several theories about the migration of haplogroups M and N once L3 left Africa and differentiated. The first is the coastal migration route for M through the Arabian, peninsula, India and on into China and thence to north east Asia. This is coupled with a presumed northern migration route for haplogroup N above the Himalayas. While this hypothesis has much evidence to support it, including the presence of L3 in Arabia and early subclades of haplogroup M in India, it would have haplogroup M reaching Beringia too late for the early entry date idea to be feasible.

However there has, recently been emerging evidence that a single wave of migration, for haplogroups M and N, via central Asia, is a distinct possibility.

To envisage the sequence of events, I have put together a simple map:

There are three stands of evidence to support this:

1. Moreno-Mayar et al. (2016) find that carriers of human mitochondrial DNA macrohaplogroup M colonized India from south eastern Asia. They base their conclusion on the fact that founder ages of M lineages in India are significantly younger than those in East Asia, Southeast Asia and Near Oceania. Moreover, there is a significant positive correlation between the age of the M haplogroups and its longitudinal geographical distribution. These results point to a colonization of the Indian subcontinent by modern humans carrying M lineages from the east instead the west side.

2. Lu et al. (2016) find that, AMH reached the Tibetan plateau much earlier than previously believed. They base this assessment on a specific 300 kb region of DNA with ‘entangled ancestries’. The authors say: “The ancestral pattern in the ~300 kb region is extremely complicated, such that it contains a mix of Denisovan, Neanderthal, ancient Siberian, and unknown archaic ancestries, which are elevated in TIB. The unusually high frequency of archaic sequences and substantial differences between TIB and HAN—as well as other worldwide populations—cannot be explained by recent gene flows or incomplete linage sorting. These highly differentiated sequences harboured in the genomes of present-day Tibetan highlanders were most likely “inherited” from earlier settlers rather than “introgressed” by later arrivers. The complicated ancestral architectures in these regions have many implications for Tibetan origins and their pre-history. The surviving archaic sequences in the ∼300 kb region trace their ancestries back to ∼62,000–38,000 years ago, pre-dating the LGM and indicating that the colonization of humans in Tibet is much more ancient than previously thought.”

3. The findings of Derenko et al. (2003), who state: “To investigate the origin and evolution of aboriginal populations of South Siberia, a comprehensive mitochondrial DNA (mtDNA) analysis of 480 individuals, representing seven Altaic-speaking populations (Altains, Khakassians, Buryats, Sojots, Tuvinians, Todjins and Tofalars) was performed… The total sample revealed 81% East Asian (M*, M7, M8, M9, M10, C, D, G, Z, A, B, F, N9a, Y) and 17% West Eurasian (H, U, J, T, I, N1a, X) matalineal genetic contribution but with regional differences in South Siberia… The considerable substructure within South Siberian haplogroups B, F and G, together with the high degree of haplogroup diversity revealed there, allows us to conclude that South Siberians carry the genetic imprint of (the) early-colonization phase of Eurasia.”

An early arrival in America – which route?

As mentioned above, there are two possibilities for migration via Beringia:

·         The Pacific coastal route (route 4)

·         Via the Ice-Free Corridor (route 5)

Admittedly, there is evidence for a Pacific coastal entry. I will leave it aside for now, and focus on the Ice-Free Corridor, as the former has been put forward due perceived (and I believe unfounded), major problems with the later.

Put simply, during the peak of the last glacial maximum two huge ice sheets, the Laurentide in the east and the Cordilleran in the west, merged, thus completely blocking an overland route to the Americas. However, with end of the last Ice Age, these ice sheets began to melt and a passageway, formed between the ice sheets. This open strip of land following the course of the McKenzie river in the North and paralleling the east side of the Rocky Mountains, further south joined the two areas of the continent, that were never glaciated.

Conventional theory has it that the Ice-Free Corridor did not re-open until after the height of the LGM. Until then it did not exist as the Laurentide and Cordilleran glaciers were fully coalesced, thus blocking any overland migration into the Americas – see map.

The coalescence of the Laurentide and Cordilleran ice sheet, blocking an overland migration into the Americas at the height of the LGM. Picture credit Earle (2015).

Ergo, the Pacific coastal route must have been the route of entry into the Americas prior to the re-opening of the Ice-Free-Corridor.

Commensurate with this idea is the Beringian Standstill theory. This would have Paleoamericans arriving in eastern Beringia (Alaska) ca. 25,000BP.

And just sitting there.

Until the Ice-Free Corridor reopened.

The timing of this event has duplicitously claimed to have only occurred, just prior to the Clovis people’s arrival. This interpretation of the timing of when the Ice-Free Corridor was open, have been brought forward to constrain human migration, to sometime around 15,000 -16,000BP.

I say duplicitously because, as has been shown, by recent research, the Ice-Free Corridor was, actually, open continuously much earlier!

The research was carried out by Lionel E. Jackson and colleagues from the universities of Alberta and New Mexico tech. It centred around the foothills erratics train, a series of exotic quartzite rocks, ranging from smaller pieces to house-sized boulders, hugging the eastern side of the Rocky Mountains in central Alberta, Canada, that has been characterised as the terminal point of the furthest, advance of the Laurentide Glacier.

In an interview with Milideo (2014) Jackson said: “It’s thought that these rocks fell onto glaciers up in the mountains and were transported out of the [Canadian Rocky] mountains into the foothills,” Jackson says. In order for them to be strung out in a straight line all along the foothills and down into Montana “they would have to represent a zone of coalescence between glaciers that came out of the mountains and the Laurentide ice sheet.”

The closing and reopening of the Ice-Free Corridor during the late Pleistocene. Picture credit: base map by NOAA NGDC; modified by Kathleen Cantner, AGI, from Earth Magazine (2014).

The technique the scientist used was Cosmogenic 36 Cl dating. This technique is based on the fact that cosmic rays, incident on the Earth’s atmosphere, mainly reach the ground as neutrons. These neutrons are absorbed, say, by erratic rocks left behind by glaciers. Radionucleotides, such as Chlorine-36 are produced. As the rate of decay of this isotope is known, as is the average cosmic radiation intensity, the length of exposure on the surface can therefore be calculated.

Jackson sampling the Foothills Erratics train. Photo credit: Earth Magazine (2104).

In fact, Jackson had been working on the problem for two decades and using this technique and had begun to publish results in the mid 1990’s – see, for example, Jackson et al. (1999): “Cosmogenic 36Cl exposure dating of erratics from the Canadian Shield on the summit of Porcupine Hills, Cloudy Ridge, and Foothills uplands south of Cardston indicates that they were deposited during the Late Wisconsinan substage.

Their ages overlap with 36Cl ages determined on erratics deposited on younger drift sheets of montane and continental provenances in the same area. This establishes the last (Laurentide) ice sheet as the most extensive of Pleistocene continental ice sheets in southwestern Alberta. This maximum limit can be stratigraphically linked to the oldest continental till known in the subsurface of the southwestern Foothills region. Thus the 36Cl ages date it as Late Wisconsinan as well.”

It has taken a long time for his work to gain any significant attention, however he has plodded on, highlighting the implications of his work more forcefully as the years have gone by. His work has also been confirmed by others (see Dyke et al., 2003; Bednarski and Smith, 2007; Andriashek et al. 2014; Hickin et al. 2016).

Further research by Jackson (2014) states that: “There is extensive and robust stratigraphic and geomorphic evidence of progressive enlargement of North American (NA) continental ice sheets in a westerly direction during successive glaciations of the Quaternary Period. This culminated in a one-time coalescence of the Laurentide Ice sheet and valley glaciers from the Rocky and Mackenzie mountains and outlet glaciers from the Cordilleran Ice Sheet during marine isotope stage (MIS) 2. This singular coast-to-coast ice (CCI) event ended the pattern of broad ice-free corridors between Cordilleran and continental glaciers that was the norm during all previous Quaternary glacial maxima in North America. Recent discoveries of human settlements above the Arctic Circle in eastern Siberia during MIS 3 (~30 C14 ky BP) and an accumulation of archaeological sites in NA south of the limit of glaciation dating to MIS 3 (specifically <30 C14 ky BP to ~22 C14 ky BP) or contemporaneous with the CCI event during MIS 2 (specifically ~22 C14 ky BP to ~14 C14 ky BP) suggest that the limiting event for initial overland human migration into the Americas was the closing of the ice-free corridor rather than its opening as has been the orthodoxy.”
Jackson has continued his work in collaboration with others, eventually showing that there have been approximately 6 advance-retreat cycles in the region in the last 800,000 years. Crucially though, there was only one coalescence of the Laurentide and Cordilleran ice sheets, at ca. 20,000BP. - see Andriashek et al. (2014).

Conclusion

In putting together this post, I have looked at a vast swathe of evidence. I must admit I am a partial researcher. I set out to see whether there was enough evidence to support an early entry into the Americas via the Ice-Free Corridor.

Having said that I am a partial investigator, and an amateur when it comes to interpreting genetic data, I believe I have put together enough evidence to show that:

1. An early entry into the Americas is possible, on the basis of, the DNA evidence.

2. An overland route via the Ice-Free Corridor route was possible at least six times since ca. 800,000BP, and that, it was in fact possible until some, time just before the Last Glacial Maximum. The exact timing of the closing of the Ice-Free Corridor being between 25,000 and 20,000BP.

3. The archaeological evidence I have reported on:

Meadowcroft Rockshelter, Pennsylvania USA (see here)

Buttermilk Creek, Texas USA (see here)

Nugget Gulch, Yukon Canada (see here)

Blue Fish Caves, Canada (see here)

Santa Elina Rock Shelter, Mato Grosso, Brazil (see here)

Cerutti Mastodon site, California USA (see here)

Also support an early entry model, via the Ice-Free Corridor.

Lastly, I must say, I do not presume to say that I have proved that my view of the facts is the correct one, no. I am merely advocating that the evidence points quite convincingly in the direction of an early entry into the Americas via the Ice-Free Corridor.

I must also give a hat-tip to Marnie Dunsmore, over at the Linear Population Model blog (see here),  for posting a recently updated map of Beringia, that was the initial inspiration for this post.

Please feel free to ‘knock holes’ in my reasoning – I welcome your comments!

References

ABC news (2015) at: https://mobile.abc.net.au/news/2015-09-22/mummys-been-the-word-for-1300-years-perus-kuelap-is-machu-picchu/6793076 accessed 12.03.19

Adnaera (2018) at: https://adnaera.com/2018/11/27/early-human-dispersals-within-the-americas-moreno-mayar-et-al-2018/ accessed 13.03.18

Achilli, Alessandro; Perego, Ugo A.; Bravi, Claudio M.; et al. (12 March 2008). "The Phylogeny of the Four Pan-American MtDNA Haplogroups: Implications for Evolutionary and Disease Studies". PLoS ONE. 3 (3): e1764.

Andriashek, L.D., Barendregt, R.W. and Jackson, L.E., 2014. Evidence for Early Pleistocene glaciation obtained from borecores collected in North-Central Alberta, Canada. Matrix, 1, p.1.

Battaglia, V., Grugni, V., Perego, U.A., Angerhofer, N., Gomez-Palmieri, J.E., Woodward, S.R., Achilli, A., Myres, N., Torroni, A. and Semino, O., 2013. The first peopling of South America: new evidence from Y-chromosome haplogroup Q. PLoS One, 8(8), p.e71390.

Bednarski, J.M., Smith, I.R., 2007. Laurentide and montane glaciations along the

Rocky Mountain Foothills in northeastern British Columbia. Canadian Journal of

Earth Sciences 44, 445e457.

Bolnick, D.A., Bolnick, D.I. and Smith, D.G., 2006. Asymmetric male and female genetic histories among Native Americans from Eastern North America. Molecular biology and evolution, 23(11), pp.2161-2174.

Bortolini, M.C., Salzano, F.M., Thomas, M.G., Stuart, S., Nasanen, S.P., Bau, C.H., Hutz, M.H., Layrisse, Z., Petzl-Erler, M.L., Tsuneto, L.T. and Hill, K., 2003. Y-chromosome evidence for differing ancient demographic histories in the Americas. The American Journal of Human Genetics, 73(3), pp.524-539.

Carpenter, M.L., Buenrostro, J.D., Valdiosera, C., Schroeder, H., Allentoft, M.E., Sikora, M., Rasmussen, M., Gravel, S., Guillén, S., Nekhrizov, G. and Leshtakov, K., 2013. Pulling out the 1%: whole-genome capture for the targeted enrichment of ancient DNA sequencing libraries. The American Journal of Human Genetics, 93(5), pp.852-864.

Derenko, M.V., Grzybowski, T., Malyarchuk, B.A., Dambueva, I.K., Denisova, G.A., Czarny, J., Dorzhu, C.M., Kakpakov, V.T., Miścicka‐Śliwka, D., Woźniak, M. and Zakharov, I.A., 2003. Diversity of mitochondrial DNA lineages in South Siberia. Annals of human genetics, 67(5), pp.391-411.

Dyke, A.S., Moore, A., Robertson, L., 2003. Deglaciation of North America. Open File

1574. Geological Survey of Canada, Ottawa.

Dziebel G., (2013) at: http://anthropogenesis.kinshipstudies.org/blog/2013/11/20/ancient-dna-from-malta-and-afontova-gora-a-full-account/ Accessed 05.03.19

Earle, S. (2015). Physical Geology by Steven Earle used under a CC-BY 4.0 International license. See: https://opentextbc.ca/geology/

Earth Magazine (2104) at: https://www.earthmagazine.org/article/fieldwork-revises-ice-free-corridor-hypothesis-human-migration accessed 18.03.19

Genetiker (2014) at: https://genetiker.wordpress.com/mt-snp-calls-for-chachapoya-sample-na40/

Gonçalves, V.F., Stenderup, J., Rodrigues-Carvalho, C., Silva, H.P., Gonçalves-Dornelas, H., Líryo, A., Kivisild, T., Malaspinas, A.S., Campos, P.F., Rasmussen, M. and Willerslev, E., 2013. Identification of Polynesian mtDNA haplogroups in remains of Botocudo Amerindians from Brazil. Proceedings of the National Academy of Sciences, 110(16), pp.6465-6469.

Hickin, A.S., Lian, O.B. and Levson, V.M., 2016. Coalescence of late Wisconsinan Cordilleran and Laurentide ice sheets east of the Rocky Mountain Foothills in the Dawson Creek region, northeast British Columbia, Canada. Quaternary Research, 85(3), pp.409-429.

Jackson, Jr, L.E., Phillips, F.M. and Little, E.C., 1999. Cosmogenic 36Cl dating of the maximum limit of the Laurentide Ice Sheet in southwestern Alberta. Canadian Journal of Earth Sciences, 36(8), pp.1347-1356.

Jackson Jr, Lionel E. (2014). "Progressive Westward Expansion of North American Continental Ice Sheets during the Quaternary and Implications for the Timing of Initial Human Overland Migration into the Americas." In 2014 GSA Annual Meeting in Vancouver, British Columbia. 2014.

Kemp, B.M. and Schurr, T.G., 2010. Ancient and modern genetic variation in the Americas. Human Variation in the Americas: The Integration of Archaeology and Biological Anthropology, pp.12-50.

Lalueza, C., Perez-Perez, A., Prats, E., Cornudella, L. and Turbon, D., 1997. Lack of founding Amerindian mitochondrial DNA lineages in extinct aborigines from Tierra del Fuego-Patagonia. Human Molecular Genetics, 6(1), pp.41-46.

Lell, J.T., Sukernik, R.I., Starikovskaya, Y.B., Su, B., Jin, L., Schurr, T.G., Underhill, P.A. and Wallace, D.C., 2002. The dual origin and Siberian affinities of Native American Y chromosomes. The American Journal of Human Genetics, 70(1), pp.192-206.

Lindo, J., Haas, R., Hofman, C., Apata, M., Moraga, M., Verdugo, R.A., Watson, J.T., Llave, C.V., Witonsky, D., Beall, C. and Warinner, C., 2018. The genetic prehistory of the Andean highlands 7000 years BP though European contact. Science advances, 4(11), p.eaau4921.

Lu, D., Lou, H., Yuan, K., Wang, X., Wang, Y., Zhang, C., Lu, Y., Yang, X., Deng, L., Zhou, Y. and Feng, Q., 2016. Ancestral origins and genetic history of Tibetan highlanders. The American Journal of Human Genetics, 99(3), pp.580-594.

Malhi and Smith, Brief Communication: Haplogroup X Confirmed in Prehistoric North America, American Journal of Physical Anthropology, Volume 119, Issue 1, (September 2002), Pages 84-86.

Malhi, Singh, R., Gonzalez‐Oliver, A., Schroeder, K.B., Kemp, B.M., Greenberg, J.A., Dobrowski, S.Z., Smith, D.G., Resendez, A., Karafet, T., Hammer, M. and Zegura, S., 2008. Distribution of Y chromosomes among native North Americans: a study of Athapaskan population history. American Journal of Physical Anthropology: The Official Publication of the American Association of Physical Anthropologists, 137(4), pp.412-424.

Merriwether DA, Rothhammer F, Ferrell RE (1995) Distribution of the four founding lineage haplotypes in Native Americans suggests a single wave of migration for the New World. Am J Phys Anthropol 98:411–430

Marrero, P., Abu-Amero, K.K., Larruga, J.M. and Cabrera, V.M., 2016. Carriers of human mitochondrial DNA macrohaplogroup M colonized India from southeastern Asia. BMC evolutionary biology, 16(1), p.246.

Moreno-Mayar, J.V., Vinner, L., de Barros Damgaard, P., de la Fuente, C., Chan, J., Spence, J.P., Allentoft, M.E., Vimala, T., Racimo, F., Pinotti, T. and Rasmussen, S., 2018. Early human dispersals within the Americas. Science, 362(6419), p.eaav2621.

Milendo, L. (2014) “Fieldwork revises ice-free corridor hypothesis of human migration” https://www.earthmagazine.org/article/fieldwork-revises-ice-free-corridor-hypothesis-human-migration

Nature News (2013). “Americas’ natives have European roots” at: https://www.nature.com/news/americas-natives-have-european-roots-1.14213 accessed 06.03.19

Neel JV, Biggar RJ, Sukernik RI (1994) Virologic and genetic studies relate Amerind origins to the indigenous people of the Mongolia/Manchuria/southeastern Siberia region. Proc Natl Acad Sci USA 91:10737–10741

Pena SDJ, Santos FR, Bianchi N, Bravi CM, Carnese FR, Rothhammer F, Gerelsaikhan T, et al (1995) Identification of a major founder Y-chromosome haplotype in Amerindians. Nat Genet 11:15–16

phylotree.org (2016) at: http://www.phylotree.org/tree/index.htm accessed 08.03.19

Posth, C., Nakatsuka, N., Lazaridis, I., Skoglund, P., Mallick, S., Lamnidis, T.C., Rohland, N., Nägele, K., Adamski, N., Bertolini, E. and Broomandkhoshbacht, N., 2018. Reconstructing the deep population history of Central and South America. Cell, 175(5), pp.1185-1197.

Raghavan, M., Skoglund, P., Graf, K.E., Metspalu, M., Albrechtsen, A., Moltke, I., Rasmussen, S., Stafford Jr, T.W., Orlando, L., Metspalu, E. and Karmin, M., 2014. Upper Palaeolithic Siberian genome reveals dual ancestry of Native Americans. Nature, 505(7481), p.87.

Rasmussen, M., Anzick, S.L., Waters, M.R., Skoglund, P., DeGiorgio, M., Stafford Jr, T.W., Rasmussen, S., Moltke, I., Albrechtsen, A., Doyle, S.M. and Poznik, G.D., 2014. The genome of a Late Pleistocene human from a Clovis burial site in western Montana. Nature, 506(7487), p.225.

Reidla M, Kivisild T, Metspalu E, Kaldma K, Tambets K, Tolk HV, et al. (Nov 2003). "Origin and diffusion of mtDNA haplogroup X". American Journal of Human Genetics. 73 (5): 1178–90.

Santos F.R., Hutz M, Coimbra CEA, Santos RV, Salzano FM, Pena SDJ (1995) Further evidence for the existence of a major founder Y chromosome haplotype in Amerindians. Braz J Genet 18:669–672

Santos, F.R., Pandya, A., Tyler-Smith, C., Pena, S.D., Schanfield, M., Leonard, W.R., Osipova, L., Crawford, M.H. and Mitchell, R.J., 1999. The central Siberian origin for native American Y chromosomes. The American Journal of Human Genetics, 64(2), pp.619-628.

Schurr, T.G., 2000. Mitochondrial DNA and the Peopling of the New World. American Scientist, 88(3), pp.246-253.

Schurr, T G., Scott W. Ballinger, Y.-Y. Gan, J. A. Hodge, D. A Merriwether, D. N. Lawrence, W. C. Knowler, K. M. Weiss, and D. C. Wallace 1990. Amerindian Mitochondrial DNAs Have Rare Asian Mutations at High Frequencies, Suggesting They Derived from Four Primary Maternal Lineages. American Journal of Human Genetics 46:613–623.

Skoglund, P., Mallick, S., Bortolini, M.C., Chennagiri, N., Hünemeier, T., Petzl-Erler, M.L., Salzano, F.M., Patterson, N. and Reich, D., 2015. Genetic evidence for two founding populations of the Americas. Nature, 525(7567), p.104.

Stanford, D.J. and Bradley, B.A., 2012. Across Atlantic ice: the origin of America's Clovis culture. Univ            of California Press.

Starikovskaya, E.B., Sukernik, R.I., Derbeneva, O.A., Volodko, N.V., Ruiz‐Pesini, E., Torroni, A., Brown, M.D., Lott, M.T., Hosseini, S.H., Huoponen, K. and Wallace, D.C., 2005. Mitochondrial DNA diversity in indigenous populations of the southern extent of Siberia, and the origins of Native American haplogroups. Annals of human genetics, 69(1), pp.67-89.

Tarazona-Santos, E. and Santos, F.R., 2002. The peopling of the Americas: a second major migration?. American journal of human genetics, 70(5), p.1377.

Torroni A, Schurr TG, Cabell MF, Brown MD, Neel JV, Larsen M, Smith DG, et al (1993) Asian affinities and continental radiation of the four founding Native American mtDNAs. Am J Hum Genet 53:563–590

White, S. V. S., 2015. The Anzick Site: Cultural Balance and the Treatment of Ancient Human Remains (Toward a Collaborative Standard).

Wikipedia commons: By Unknown - Российский Этнографический музей (The Russian Museum of Ethnography)., https://commons.wikimedia.org/w/index.php?curid=1602174

Wong, E.H., Khrunin, A., Nichols, L., Pushkarev, D., Khokhrin, D., Verbenko, D., Evgrafov, O., Knowles, J., Novembre, J., Limborska, S. and Valouev, A., 2017. Reconstructing genetic history of Siberian and Northeastern European populations. Genome research, 27(1), pp.1-14.

Yang, M.A., Gao, X., Theunert, C., Tong, H., Aximu-Petri, A., Nickel, B., Slatkin, M., Meyer, M., Pääbo, S., Kelso, J. and Fu, Q., 2017. 40,000-year-old individual from Asia provides insight into early population structure in Eurasia. Current Biology, 27(20), pp.3202-3208.

Yang, M.A. and Fu, Q., 2018. Insights into modern human prehistory using ancient genomes. Trends in Genetics, 34(3), pp.184-196.

Zegura, S.L., Karafet, T.M., Zhivotovsky, L.A. and Hammer, M.F., 2004. High-resolution SNPs and microsatellite haplotypes point to a single, recent entry of Native American Y chromosomes into the Americas. Molecular biology and evolution, 21(1), pp.164-175.