This week has seen a flurry of new scientific and news articles. What has been causing such a stir? It appears that Australian or more accurately, Australo-Melanese DNA has been found in South America’s Native American population. In addition, it has also been found in Aleutian Islanders off the coast of Alaska. In case you aren’t aware, that’s about 8,500 miles as the crow flies. That’s one tired crow. As the person paddles or walks along the shoreline, it’s even further, probably about 12,000 miles.
Whatever the story, it was quite a journey and it certainly wasn’t all over flat land.
This isn’t the first inkling we’ve had. Just a couple weeks ago, it was revealed that the Botocudo remains from Brazil were Polynesian and not admixed with either Native, European or African. This admixture was first discovered via mitochondrial DNA, but full genome sequencing confirmed their ancestry and added the twist that they were not admixed – an extremely unexpected finding. This is admittedly a bit confusing, because it implies that there were new Polynesian arrivals in the 1600s or 1700s.
Unlikely as it seems, it obviously happened, so we set that aside as relatively contemporary.
The findings in the papers just released are anything but contemporary.
The First Article
The first article in Science, “Genomic evidence for the Pleistocene and recent population history of Native Americans” by Raghaven et al published this week provides the following summary (bolding is mine):
How and when the Americas were populated remains contentious. Using ancient and modern genome-wide data, we find that the ancestors of all present-day Native Americans, including Athabascans and Amerindians, entered the Americas as a single migration wave from Siberia no earlier than 23 thousand years ago (KYA), and after no more than 8,000-year isolation period in Beringia. Following their arrival to the Americas, ancestral Native Americans diversified into two basal genetic branches around 13 KYA, one that is now dispersed across North and South America and the other is restricted to North America. Subsequent gene flow resulted in some Native Americans sharing ancestry with present-day East Asians (including Siberians) and, more distantly, Australo-Melanesians. Putative ‘Paleoamerican’ relict populations, including the historical Mexican Pericúes and South American Fuego-Patagonians, are not directly related to modern Australo-Melanesians as suggested by the Paleoamerican Model.
This article in EurekAlert and a second one here discuss the Science paper.
Migration map from the Raghaven paper.
The paper included the gene flow and population migration map, above, along with dates.
The scientists sequenced the DNA of 31 living individuals from the Americas, Siberia and Oceana as follows:
- Altai – 2
- Buryat – 2
- Ket – 2
- Kiryak – 2
- Sakha – 2
- Siberian Yupik – 2
North American Native:
- Tsimshian (number not stated, but by subtraction, it’s 1)
Southern North American, Central and South American Native:
- Pima – 1
- Huichol -1
- Aymara – 1
- Yakpa – 1
The researchers also state that they utilized 17 specimens from relict groups such as the Pericues from Mexico and Fuego-Patagonians from the southernmost tip of South America. They also sequenced two pre-Columbian mummies from the Sierra Tarahumara in northern Mexico. In total, 23 ancient samples from the Americas were utilized.
They then compared these results with a reference panel of 3053 individuals from 169 populations which included the ancient Saqqaq Greenland individual at 400 years of age as well as the Anzick child from Montana from about 12,500 years ago and the Mal’ta child from Siberia at 24,000 years of age.
Not surprisingly, all of the contemporary samples with the exception of the Tsimshian genome showed recent western Eurasian admixture.
As expected, the results confirm that the Yupik and Koryak are the closest Eurasian population to the Americas. They indicate that there is a “clean split” between the Native American population and the Koryak about 20,000 years ago.
They found that “Athabascans and Anzick-1, but not the Greenlandis Inuit and Saqqaq belong to the same initial migration wave that gave rise to present-day Amerindians from southern North America and Central and South America, and that this migration likely followed a coastal route, given our current understanding of the glacial geological and paleoenvironmental parameters of the Late Pleistocene.”
Evidence of gene flow between the two groups was also found, meaning between the Athabascans and the Inuit. Additionally, they found evidence of post-split gene flow between Siberians and Native Americans which seems to have stopped about 12,000 years ago, which meshes with the time that the Beringia land bridge was flooded by rising seas, cutting off land access between the two land masses.
They state that the results support all Native migration from Siberia, contradicting claims of an early migration from Europe.
The researchers then studied the Karitiana people of South America and determined that the two groups, Athabascans and Karitiana diverged about 13,000 years ago, probably not in current day Alaska, but in lower North America. This makes sense, because the Clovis Anzick child, found in Montana, most closely matches people in South America.
By the Clovis period of about 12,500 years ago, the Native American population had already split into two branches, the northern and southern, with the northern including Athabascan and other groups such as the Chippewa, Cree and Ojibwa. The Southern group included people from southern North America and Central and South America.
Interestingly, while admixture with the Inuit was found with the Athabascan, Inuit admixture was not found among the Cree, Ojibwa and Chippewa. The researchers suggest that this may be why the southern branch, such as the Karitiana are genetically closer to the northern Amerindians located further east than to northwest coast Amerindians and Athabascans.
Finally, we get to the Australian part. The researchers when trying to sort through the “who is closer to whom” puzzle found unexpected results. They found that some Native American populations including Aleutian Islanders, Surui (Brazil) and Athabascans are closer to Australo-Melanesians compared to other Native Americans, such as Ojibwa, Cree and Algonquian and South American Purepecha (Mexico), Arhuaco (Colombia) and Wayuu (Colombia, Venezuela). In fact, the Surui are one of the closest populations to East Asians and Australo-Melanese, the latter including Papuans, non-Papuan Melanesians, Solomon Islanders and hunter-gatherers such as Aeta. The researchers acknowledge these are weak trends, but they are nonetheless consistently present.
Dr. David Reich, from Harvard, a co-author of another paper, also published this past week, says that 2% of the DNA of Amazonians is from Oceana. If that is consistent, it speaks to a founder population in isolation, such that the 2% just keeps getting passed around in the isolated population, never being diluted by outside DNA. I would suggest that is not a weak signal.
The researchers suggest that the variance in the strength of this Oceanic signal suggests that the introduction of the Australo-Melanese occurred after the initial peopling of the Americas. The ancient samples cluster with the Native American groups and do not show the Oceanic markers and show no evidence of gene flow from Oceana.
The researchers also included cranial morphology analysis, which I am omitting since cranial morphology seems to have led researchers astray in the past, specifically in the case of Kennewick man.
One of the reasons cranial morphology is such a hotly debated topic is because of the very high degree of cranial variance found in early skeletal remains. One of the theories evolving from the cranial differences involving the populating of the Americans has been that the Australo-Melanese were part of a separate and earlier migration that gave rise to the earliest Americans who were then later replaced by the Asian ancestors of current day Native Americans. If this were the case, then the now-extinct Fuego-Patagonains samples from the location furthest south on the South American land mass should have included DNA from Oceana, but it didn’t.
The Second Article
A second article published this week, titled “’Ghost population’ hints at long lost migration to the Americas” by Ellen Callaway discusses similar findings, presented in a draft letter to Nature titled “Genetic evidence for two founding populations of the Americas” by Skoglund et al. This second group discovers the same artifact Australo-Melanesian DNA in Native American populations but suggests that it may be from the original migration and settlement event or that there may have been two distinct founding populations that settled at the same time or that there were two founding events.
EurekAlert discusses the article as well.
It’s good to have confirmation and agreement between the two labs who happened across these results independently that the Australo-Melanesian DNA is present in some Native populations today.
Their interpretations and theories about how this Oceanic DNA arrived in some of the Native populations vary a bit, but if you read the details, it’s really not quite as different as it first appears from the headlines. Neither group claims to know for sure, and both discuss possibilities.
Questions remain. For example, if the founding group was small, why, then, don’t all of the Native people and populations have at least some Oceanic markers? The Anzick Child from 12,500 years ago does not. He is most closely related to the tribes in South America, where the Oceanic markers appear with the highest frequencies.
In the Harvard study, the scientists fully genome sequenced 63 individuals without discernable evidence of European or African ancestors in 21 Native American populations, restricting their study to individuals from Central and South America that have the strongest evidence of being entirely derived from a homogenous First American ancestral population.
Their results show that the two Amazonian groups, Surui and Karitians are closest to the “Australasian populations, the Onge from the Andaman Island in the Bay of Bengal (a so-called ‘Negrito’ group), New Guineans, Papuans and indigenous Australians.” Within those groups, the Australasian populations are the only outliers – meaning no Africans, Europeans or East Asian DNA found in the Native American people.
When repeating these tests, utilizing blood instead of saliva, a third group was shown to also carry these Oceanic markers – the Xavante, a population from the Brazilian plateau that speaks a language of the Ge group that is different from the Tupi language group spoke by the Karitians and Surui.
The closest populations that these Native people matched in Oceana, shown above on the map from the draft Skoglund letter, were, in order, New Guineans, Papuans and Andamanese. The researchers further state that populations from west of the Andes or north of the Panama isthmus show no significant evidence of an affinity to the Onge from the Andaman Islands with the exception of the Cabecar (Costa Rica).
That’s a very surprising finding, given that one would expect more admixture on the west, which is the side of the continent where the migration occurred.
The researchers then compared the results with other individuals, such as Mal’ta child who is known to have contributed DNA to the Native people today, and found no correlation with Oceanic DNA. Therefore, they surmised that the Oceanic admixture cannot be explained by a previously known admixture event.
They propose that a mystery population they have labeled as “Population Y” (after Ypykuera which means ancestor in the Tupi language family) contributed the Australasian lineage to the First Americans and that is was already mixed into the lineage by the time it arrived in Brazil.
According to their work, Population Y may itself have been admixed, and the 2% of Oceanic DNA found in the Brazilian Natives may be an artifact of between 2 and 85% of the DNA of the Surui, Karitiana and Xavante that may have come from Population Y. They mention that this result is striking in that the majority of the craniums that are more Oceanic in Nature than Asiatic, as would be expected from people who migrated from Siberia, are found in Brazil.
They conclude that the variance in the presence or absence of DNA in Native people and remains, and the differing percentages argue for more than one migration event and 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.”
Perhaps even more interesting is the following statement:
“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.”
They further state they find no admixture indication that would suggest that Population Y arrived in the last few thousand years.
So, it appears that perhaps the Neanderthals and Denisovans were not the only people who were our ancestors, but no longer exist as a separate people, only as an admixed part of us today. We are their legacy.
The Take Away
When I did the Anzick extractions, we had hints that something of this sort might have been occurring. For example, I found surprising instances of haplogroup M, which is neither European, African nor Native American, so far as we know today. This may have been a foreshadowing of this Oceanic admixture. It may also be a mitochondrial artifact. Time will tell. Perhaps haplogroup M will turn out to be Native by virtue of being Oceanic and admixed thousands of years ago. There is still a great deal to learn. Regardless of how these haplogroups and Oceanic DNA arrived in Brazil in South America and in the Aleutian Islands off of Alaska, one thing is for sure, it did.
We know that the Oceanic DNA found in the Brazilian people studied for these articles is not contemporary and is ancient. This means that it is not related to the Oceanic DNA found in the Botocudo people, who, by the way, also sport mitochondrial haplogroups that are within the range of Native people, meaning haplogroup B, but have not been found in other Native people. Specifically, haplogroups B4a1a1 and B4a1a1a. Additionally, there are other B4a1a, B4a1b and B4a1b1 results found in the Anzick extract which could also be Oceanic. You can see all of the potential and confirmed Native American mitochondrial DNA results in my article “Native American Mitochondrial Haplogroups” that I update regularly.
We don’t know how or when the Botocudo arrived, but the when has been narrowed to the 1600s or 1700s. We don’t know how or when the Oceanic DNA in the Brazilian people arrived either, but the when was ancient. This means that Oceanic DNA has arrived in South America at least twice and is found among the Native peoples both times.
We know that some Native groups have some Oceanic admixture, and others seem to have none, in particular the Northern split group that became the Cree, Ojibwa, Algonquian, and Chippewa.
We know that the Brazilian Native groups are most closely related to Oceanic groups, but that the first paper also found Oceanic admixture in the Aleutian Islands. The second paper focused on the Central and South American tribes.
We know that the eastern American tribes, specifically the Algonquian tribes are closely related to the South Americans, but they don’t share the Oceanic DNA and neither do the mid-continent tribes like the Cree, Ojibwa and Chippewa. The only Paleolithic skeleton that has been sequenced, Anzick, from 12,500 years ago in Montana also does not carry the Oceanic signature.
In my opinion, the disparity between who does and does not carry the Oceanic signature suggests that the source of the Oceanic DNA in the Native population could not have been a member of the first party to exit out of Beringia and settle in what is now the Americas. Given that this had to be a small party, all of the individuals would have been thoroughly admixed with each other’s ancestral DNA within just a couple of generations. It would have been impossible for one ancestor’s DNA to only be found in some people. To me, this argues for one of two scenarios.
First, a second immigration wave that joined the first wave but did not admix with some groups that might have already split off from the original group such as the Anzick/Montana group.
Second, multiple Oceanic immigration events. We still have to consider the possibility that there were multiple events that introduced Oceanic DNA into the Native population. In other words, perhaps the Aleutian Islands Oceanic DNA is not from the same migration event as the Brazilian DNA which we know is not from the same event as the Botocudo. I would very much like to see the Oceanic DNA appear in a migration path of people, not just in one place and then the other. We need to connect the dots.
What this new information does is to rule out the possibility that there truly was only one wave of migration – one group of people who settled the Americas at one time. More likely, at least until the land bridge submerged, is that there were multiple small groups that exited Beringia over the 8,000 or so years it was inhabitable. Maybe one of those groups included people from Oceana. Someplace, sometime, as unlikely as it seems, it happened.
The amazing thing is that it’s more than 10,000 miles from Australia to the Aleutian Islands, directly across the Pacific. Early adventurers would have likely followed a coastal route to be sustainable, which would have been significantly longer. The fact that they survived and sent their DNA on a long adventure from Australia to Alaska to South America – and it’s still present today is absolutely amazing.
We know we still have a lot to learn and this is the tip of a very exciting iceberg. As more contemporary and ancient Native people have their full genomes sequenced, we’ll learn more answers. The answer is in the DNA. We just have to sequence enough of it and learn how to understand the message being delivered.