A new paper published in the Proceedings of the National Academy of Sciences has announced the discovery of the youngest known human remains ever found in the Arctic – two Ice Age babies that were buried more than 11,000 years ago in Alaska. The discovery sheds lights on ancient funerary practices in the region and provides a unique insight into the cultural practices of North America’s early inhabitants.
Ben Potter, an anthropologist at the University of Alaska Fairbanks, led the research in cooperation with local and regional indigenous organizations. The new finding was made at the site of an earlier 2010 excavation in the Upward Sun River region of central Alaska, where the cremated remains of a 3-year-old had previously been found.
The Upward Sun River site is believed to have been occupied by the Denali people who inhabited central Alaska from 12,000 to 6,000 years ago, toward the end of the Pleistocene epoch, often referred to as the last Ice Age.
Ben Potter and colleague Joshua Reuther excavate the burial of two infants at Upward Sun River in Alaska. Credit: Ben Potter
The remains of the two babies were found in a pit below a hearth in a seasonal house where the 3-year-old had been found. Experts claim that the first infant died shortly after birth and the other was a late-term foetus. It’s possible they could have been twins. Evidence suggests they had been curled up in an upright position, wrapped, and covered in red ochre.
Within the pit, archaeologists found grave offerings consisting of projectile points and sharpened stones covered in red ochre, antler rods decorated with carved lines, and plant and animal remains, including salmon-like fish and ground squirrels.
Stone projectile points and decorated antler rods from the burial pit in Alaska. Credit: Ben Potter
"The deaths occurred during the summer, a time period when regional resource abundance and diversity was high and nutritional stress should be low, suggesting higher levels of mortality than may be expected give our current understanding" of survival strategies of the period, the authors write.
The site and its artifacts provide new insights into funeral practices and other rarely preserved aspects of life among people who inhabited the area thousands of years ago, including how they treated the youngest members of their society, and how they viewed death and the importance of rituals associated with it.
However, it also poses a bit of a mystery: Why were the two infants buried intact while the third child was cremated? Archaeologists have suggested that it could be a seasonal difference, or it is possible they treated the dead differently based on age. Another theory is that a prominent family member might have been absent when the three-year-old died, causing the family to choose a simpler cremation.
“Prior to these finds, we really did not have evidence of that facet of settlement and tradition systems for the early Americans who once inhabited this area,” says Potter. “These are new windows into these ancient peoples’ lifestyle.”
Featured image: Paleo-Indians burying the deceased. Painting by Frank Weir ( Texas Beyond History )
Ancient Infant's DNA Reveals New Clues to How the Americas Were Peopled
Her 11,500-year-old remains suggest that all Native Americans can trace their ancestry to the same founding population.
Around 11,500 years ago, at a place that is now called the Upward Sun River, in the region that has since been named Alaska, two girls died. One was a late-term fetus the other, probably her cousin, was six weeks old. They were both covered in red ochre and buried in a circular pit, along with hunting weapons made from bones and antlers. “There was intentionality in the burial ceremony,” says Ben Potter from the University of Alaska at Fairbanks, who uncovered their skeletons in 2013. “These were certainly children who were well-loved.”
Now, several millennia after their short lives ended, these infants have become important all over again. Within their DNA, Potter’s team has found clues about when and how the first peoples came to the Americas.
They did so from East Asia—that much is clear. Today, Russia and Alaska are separated by the waters of the Bering Strait. But tens of thousands of years ago, when sea levels were lower, that gap was bridged by continuous land, hundreds of miles wide and covered in woodlands and meadows. This was Beringia. It was a harsh world, but you could walk across it—and people did.
The Upward Sun River infants, who have been named Xach’itee’aanenh T’eede Gaay” (Sunrise Girl-Child) and “Yełkaanenh T’eede Gaay” (Dawn Twilight Girl-Child) by the local indigenous community, were found at a crucial point along this route. Few human remains have been found from such a northerly or westerly part of the Americas, or from such an ancient time. “It’s hard to impress upon you how rare they are,” says Potter. “The window into the past that these children provide is priceless.”
By analyzing the older infant’s genome, Potter and his colleagues, including José Víctor Moreno Mayar and Lasse Vinner, have shown that she belonged to a previously unknown group of ancient people, who are distinct from all known Native Americans, past and present. The team have dubbed them the Ancient Beringians.
“We’d always suspected that these early genomes would have important stories to tell us about the past, and they certainly didn’t disappoint,” says Jennifer Raff from the University of Kansas, who was not involved in the study.
By comparing Xach’itee’aanenh T’eede Gaay’s genome to those of other groups, the team showed that the Ancient Beringians and other Native Americans descend from a single founding population that started to split away from other East Asians around 36,000 years ago. They became fully separated between 22,000 and 18,000 years ago, and then split into two branches themselves. One gave rise to the Ancient Beringians. The other gave rise to all other Native Americans, who expanded into the rest of the Americas. Native Americans, then, diverged into two more major lineages—a northern and a southern one—between 14,600 and 17,500 years ago.
This story unequivocally supports the so-called Beringian standstill hypothesis, “which for a long time has been the dominant explanation for how people initially peopled the Americas,” says Raff. This scenario says that the ancestors of Native Americans diverged from other East Asians at a time when ice was smothering the Northern Hemisphere. That left them stranded and isolated for millennia somewhere outside the Americas, for their eastward movements were blocked by a giant ice sheet that covered much of North America. Only when that sheet started melting, around 15,000 years ago, could they start migrating down the west coast of the Americas.
Xach’itee’aanenh T’eede Gaay’s genome anchors this narrative in time, suggesting that the millennia-long pit stop took place between 14,000 and 22,000 years ago. It doesn’t, however, say where those early peoples stood still.
In one scenario, they paused in Beringia itself and split into two lineages there. One, the Ancient Beringians, stayed put. The other eventually made it further east and south and gave rise to the other Native Americans. If that’s right, “there was just a single migration of people from Asia who peopled the New World,” says Connie Mulligan from the University of Florida. She and others have found further evidence for that idea, but “this study provides the final piece needed to prove there was only a single migration,” she says.
But Potter prefers an alternative scenario in which the standstill took place further back in northeast Asia, and the Ancient Beringians split from other Native Americans there. Both groups then independently traveled into Beringia and subsequently into the Americas, perhaps by different routes or perhaps at different times.
Partly, this debate hinges on a controversial archeological site at the Bluefish Caves in Canada’s Yukon Territory. A recent study says that animal bones from the site, which seem to bear traces of human cut-marks, are 24,000 years old. Raff accepts the Bluefish evidence Potter doesn’t. If the marks really were made by humans, and really are that old, people must have been in Beringia by that point, and likely paused there. If they’re not . the find doesn’t really rule out either hypothesis.
Either way, both scenarios can now be tested with future data from either ancient DNA or archaeological finds. And both scenarios argue against an attention-grabbing study from last year which claimed that hominids were in North America 130,000 years ago, based on the bones of a mastodon that had supposedly been butchered with nearby stone tools. “I am super skeptical about that,” says Potter. “Early modern humans aren’t even out of Africa at that point, so you’d be talking about, I don’t know, a Denisovan? And there are no Denisovans within 10,000 miles of that site.”
It’s also unclear what became of the Ancient Beringians. They have no obvious direct descendants, and the people who currently live at the Upward Sun River—the Athabascans—are descended from one of the other groups of Native Americans. It’s possible that the Athabascans may carry traces of Ancient Beringian ancestry, but it’s hard to say without analyzing their genomes.
Ancient baby’s DNA reveals completely unknown branch of Native American family tree
An Alaskan baby buried 11,500 years ago has clued scientists in to a forgotten branch of the Native American family tree. This child’s DNA is more genetically ancient than the ancestors of modern Native Americans — so it must have come from a previously unknown, even earlier population, the study says.
By analyzing the infant’s genome, researchers from the University of Alaska Fairbanks and the University of Copenhagen found that while all ancient Native Americans originated in East Asia, the family tree branched roughly 20,000 years ago. One group — the infant’s group, now named the Ancient Beringians — lived in the frozen north and eventually disappeared. The other moved south, splitting yet again roughly 15,000 years ago into two distinct populations that peopled North and South America.
We already knew the broad strokes of this story: ancient humans from Siberia probably crossed the Bering land bridge into Alaska sometime before 15,000 years ago. These ancient humans then spread, giving rise to most of the indigenous peoples of the Americas. Today’s study, published in the journal Nature, helps fill in more details about the genetic origins of Native Americans — and reveals a newly discovered group of ancient people.
“If you could ask for ancient DNA for Christmas, this is what you would ask for,” says Joshua Schraiber, a population geneticist at Temple University who did not take part in the study. “It gives you a much better window into population structure back then.”
In 2010, archaeologists led by Ben Potter at the University of Alaska Fairbanks unexpectedly discovered the ancient, cremated remains of a 3-year-old child at an archaeological site in central Alaska, called Upward Sun River. About a meter beneath the hearth, two infants were also buried in a circular pit filled with grave goods, including blades and hunting tools. Today’s study involves DNA extracted from one of the babies found in that pit in 2013.
The excavation of one of the ancient infants buried at the Upward River Sun site in Alaska. Photo by Ben Potter
From their bones, the researchers estimated that one of the infants in the burial pit had been about six weeks old when it passed away, and the other was likely stillborn. Radiocarbon dating revealed that all three were roughly 11,500 years old. “We’re very lucky to have these preserved,” Potter says. “We’re treating them very respectfully and letting them provide a window into their prehistory, and past, and lifeways in ways that are unparallelled.”
Now, a team of scientists led by ancient DNA specialist Eske Willerslev at the University of Copenhagen has sequenced the complete genome of the 6-week-old infant — named “Xach’itee’aanenh T’eede Gaay” (sunrise girl-child) by the local indigenous community. The DNA of the other children had degraded too much for a full sequence, although there was enough to determine that the two babies buried together may have been cousins.
By comparing the ancient infant’s genome to those collected from other ancient and modern people, the team was able to reconstruct how it fit into the human family tree. They discovered that this infant was related to the founding population of Native Americans that originated in Siberia.
Adding this new clue to computer simulations of the peopling of North America helped the team flesh out the timeline — which they now suspect goes something like this: about 36,000 years ago in northeast Asia, the ancestors of modern Native Americans began splitting off from ancestral Asians. They continued to mingle and swap genes with other Asian populations until roughly 25,000 years ago, when they became genetically cut off from the rest of Asia.
Here’s where it gets a little murky: today’s study shows that around 20,000 years ago, the Ancient Beringians branched off from the ancestors of modern Native Americans. But the researchers don’t know where exactly that Ancient Beringian split happened: it might have been in Siberia. If so, then the two populations then migrated separately into the New World. It’s also possible, though, that a single founding population may have migrated into Beringia and lingered there long enough for the two lineages to branch apart. The Ancient Beringians then stayed in the icy north, and the ancestors of modern Native Americans moved south to eventually people North and South America.
The findings show that even one new genome can reshape our understanding of ancient human history, says Joshua Akey, a professor of evolutionary genomics at Princeton University who was not involved in the research. “It shows the power of ancient DNA — how much of our history is written in our DNA.”
These two hypotheses still need to be tested with archaeology, genetics, and new human remains — if they’re discovered. “This just opens up doors that hardly ever get opened, to understand in real, meaningful ways the ancient past,” Potter says. “It's all part and parcel with the human experience. But I have to say, I did not expect that it would be as rich and rewarding as it has been.”
North Americans Were Salmon Fishing 11,500 Years Ago
Researchers studying 11,500-year-old fish bones have discovered the oldest evidence of salmon fishing in North America. According to their findings, published in Proceedings of the National Academy of Sciences this week, salmon spawning runs had been established by the end of the last Ice Age.
Paleoindians have been traditionally considered big-game hunters, though their use of fish and other resources have been difficult to determine because of the lack of preserved remains. These days, millions of salmon migrate from the ocean to spawn (and die) in their natal rivers and lakes. But many of those rivers used to be blocked by glacial ice, which severely restrict salmon ranges. However, there may have been a potential glacial refugium: Beringia, the mostly ice-free land bridge between Asia and Alaska.
Now, fish bones dating back 11,500 years have been discovered at the Upward Sun River site in interior Alaska around 1,400 kilometers (870 miles) upriver from the coast. The site is 50 kilometers (31 miles) downstream from the modern limit of major spawning areas. Based on the appearance of the vertebrae, researchers believe that they’re salmon from the genus Oncorhynchus. They recovered 308 Oncorhynchus specimens and the cremated remains of three-year-old child from the central hearth of a residence. A double infant burial with grave goods were found 40 centimeters (16 inches)ꂾlow the hearth. And an additional 29 fragmented, mostly burned salmon specimens were found within the pit fill.
By conducting ancient DNA (aDNA) analyses on two of the unburned vertebrae, a team led by Carrin Halffman from the University of Alaska Fairbanks identified the fish as chum salmon (Oncorhynchus keta). The team also conducted stable isotope analyses on one of the vertebrae, and they determined that the salmon had migrated upriver from the sea. Isotope ratios of carbon and nitrogen are typically higher in marine compared with freshwater food consumers.
The location of the remains – at the margins of modern salmon habitat – suggests that salmon spawning runs were established at least as early as the end of the last Ice Age. These remains also predate any known human uses of salmon in North America – suggesting that salmon may have been a factor in human expansion into the continent’s northwest region.
Upward Sun River stratigraphy, chronology, and aDNA and stable isotope bone samples. C.M. Halffman et al., 2015 PNAS
Today I and my collaborators have a new paper published in PNAS! Justin Tackney, the lead author of the paper, was kind enough to write up a summary of the findings to publish here on Violent Metaphors. Here is his take:
The genetic characterization of the ancestral population in Beringia for the initial peopling event into North and South America has been limited by the lack of human remains buried at the right time and place. We report on two mitochondrial genomes (mitogenomes) from the Upward Sun River site in Alaska dated to about 11,500 years ago. This site is located in what was then eastern Beringia, and was occupied only a few thousand years after the main migration south, through an inland route, along the pacific coast, or both, about 15,000 years ago. The populations living at Upward Sun River at that time might represent a residual group that subsequently left or disappeared from the region today.
With the permission and support of the Healy Lake Tribal Council and Tanana Chiefs Conference, we obtained DNA from the remains of two individuals buried at the site. One was an infant just a few weeks old. The other was a late pre-term fetus.
Tackney et al. 2015 Figure 1. Geographic map of reported Native American populations with >40% C1 or B2 haplogroup frequencies, as well as locations of archaeological sites
discussed. The locations of the Upward Sun River site, as well as the seven previously reported archaeological sites dated at >8,000 y B.P. with successfully genotyped human mitochondrial DNA lineages, are listed on the map (with reported haplotypes). Reported populations of ≥ 20 individuals with ≥ 40% C1 (yellow) or B2 (blue)
While the two remains were initially believed by archaeologists to be maternally related, the infant and the pre-term fetus carried two different mitochondrial ‘haplotypes’, or mitochondrial DNA variants. This is significant because mitochondrial DNA is only maternally inherited, so it means that they did not share a mother. Both haplotypes, C1b and B2, are rare or absent in Northern North America today (although Jennifer, Dennis, and I did find B2 present in a
1000 YBP population from the Brooks River area of the Alaska Peninsula in a previous paper*, suggesting that it was once more common in Alaska) and both were determined to be phylogenetically within or near the roots of their respective clades.
That these haplotypes were so far north at this very early date supports the Beringian Standstill Hypothesis (the idea that people lived in Beringia for at least several thousand years before moving southward into the Americas) by providing evidence for the ancestral root variants in the initial source population and by showing large genetic variation even within one residential complex. There was a third cremated 3-year old child found above the burial, dated to about the same time as the two human remains analyzed, but the cremation seems to have prevented the preservation of any DNA.
We were able to use the two precisely dated remains to inform the rate of the molecular clock within these two lineages and re-date the time to most recent common ancestor for all known Native American variants within these haplotypes. Our dates were on the younger side of recent estimates for these two clades (C1 and B2), but were close to previous dates calculated with a molecular clock also estimated with ancient DNA. We estimated C1b to coalesce at 12,854 (11,853-14,079) years before present and B2 to coalesce at 12,024 (11,500-14,085) years before present. These younger coalescence dates might be used to support a much shorter period of isolation in Beringia, as suggested by Raghavan and colleagues** earlier this year.
Our two mitogenomes are only the 8 th and 9 th mitochondrial lineages determined from human remains in the Americas dating to greater than 8,000 years ago and we are one of only 3 sites where the whole mitochondrial genome was sequenced completely. The two individuals at Upward Sun River are the farthest north human remains thus far discovered.
We performed hybridization capture for mitochondrial DNA molecules and then sequenced the captured ancient DNA on an Ion Proton system we are one of the first groups in our field to use Ion technology for this purpose.
Do you have any questions for the research team? Leave them in the comments below, and either Jennifer or Justin will answer them.
*Raff JA, Tackney JT, O’Rourke DH. 2010. South from Alaska: A pilot aDNA study of genetic history on the Alaska Peninsula and the Eastern Aleutians. Human Biology 42 (5-6): 677-693.
Mysteries Of The Black Death, Shroud Of Turin, And Origins of Early Americans Solved With DNA
While ancient DNA studies have been increasing in recent years with the advent of NextGen sequencing techniques and methods for removing modern contamination, this past week has brought incredible news that highlights the range of applications of aDNA in solving historical questions. From the first evidence of the Black Death to the continued controversy over the authenticity of the Shroud of Turin to the hypothesis that people migrated through Beringia to get to the Americas for the first time, aDNA studies published this month hold both new answers and enormous potential for archaeology.
Yamnaya people moved into Central Asia from the region around present day Caucasus in early Bronze . [+] Age (c. 5000 years ago) and developed the Afanasievo culture. The Afanasievo are one of the Bronze Age groups carrying Y. pestis. Credit: Natalia Shishlina, via Phys.org press release.)
Was the Black Death an unfortunate mutation?
The bacterium that caused the Black Death - Yersinia pestis - is actually a genetically mutated version that allowed it to reside in the guts of fleas. The disease was spread through fleas and rats in Medieval Europe, resulting in nearly half the population succumbing to bubonic plague in the 14th century. In an article published a week ago in the journal Cell, researchers traced back the evolutionary lineage of Y. pestis by studying the skeletons of 101 people from the Bronze Age. They found evidence of the bacterium in seven adults. Even more importantly, one of those people died over 5,700 years ago. The oldest previous evidence of Y. pestis in skeletons comes from someone who died just 1,500 years ago. Many of the pandemics discussed in historical records might therefore be attributable to Y. pestis.
Interestingly, when the researchers looked more closely at the Y. pestis genomes, they noticed the absence of two genetic components that are present in more contemporary samples of the bacterium. One of the mutations in the Medieval and modern Y. pestis genomes allows the bacterium to multiply in the flea's guts without being destroyed, causing the flea to bite anything it can while the other mutation lets Y. pestis spread across different tissues, meaning an infection in the lungs can spread to the blood and lymphatic systems.
What this means is that these Bronze Age strains of the plague could not have been carried by fleas and could not have caused the bubonic form of the plague that was particularly deadly in Medieval Europe. The mechanism of transmission in the Bronze Age was instead human-to-human transmission, much like the way tuberculosis is spread.
Co-author Robert Foley said in a press release that "the endemic nature of pneumonic plague was perhaps more adapted for an earlier Bronze Age population. Then, as Eurasian societies grew in complexity and trading routes continued to open up, maybe the conditions started to favor the more lethal form of plague. The Bronze Age is the edge of history, and ancient DNA is making what happened at this critical time more visible." Another co-author, Eske Willerslev, added that "these results show that the ancient DNA has the potential not only to map our history and prehistory, but also discover how disease may have shaped it."
An illustration of an 11,500-year-old grave in central Alaska that contained a rare double burial of . [+] two infants. Outlines of the two sets of remains are shown at left and center. Also found in the grave were a stone cutting tool, above center, and animal antlers with spear points, right of center. (Illustration courtesy of Ben Potter, UAF.)
Discovering the Origins of the First Americans
Yesterday, a group of researchers headed by Justin Tackney published a paper in the Proceedings of the National Academy of Sciences on ancient DNA analysis from two infant burials in Alaska that date back at least 11,500 years. Archaeologists have long known from stone tools and other remains that one or more waves of migrants crossed the dry Bering Strait between modern-day Russia and Alaska many millennia ago, working their way south into Canada, the US, and Central and South America. While the scale and number of migrations is still not entirely clear, as there would appear to have been numerous migration events over the years, Beringia -- which refers to the entire area on either side of the Strait -- is becoming a key geographical area in the search for answers about Homo sapiens' migration into the New World.
One of the main barriers to answering questions about early human migrations in this area is in finding human skeletal remains from the correct time period that have been well preserved. Tackney and colleagues got permission from the Healy Lake Tribal Council and the Tanana Chiefs Conference to do genetic testing on two burials -- an infant who was just a few weeks old and a pre-term fetus -- from the site of Upward Sun River in Alaska. They also attempted to test a 3-year-old who had been cremated, but DNA did not survive from that burial.
Mitochondrial DNA gave the team their first surprise: the infants were not maternally related, as was assumed based on the burial. Their DNA haplotypes, or maternal lineages, are very rare in northern North America. Coupled with the fact that these genetic markers are found far north at a very early date, Tackney and colleagues believe this supports the Beringian Standstill Hypothesis, which says that once people crossed over to Alaska, they stayed there for a while before migrating south. Since these two individuals are the farthest north skeletons ever discovered, their dates of death and particular mitochondrial DNA sequences add considerably to a currently very small data set of ancient DNA from the earliest settlers of Beringia.
In this pool photo taken Sunday, June 21, 2015, and made available Monday, June 22, Pope Francis . [+] prays in front of the Holy Shroud, the 14 foot-long linen revered by some as the burial cloth of Jesus, on display at the Cathedral of Turin, Italy, Sunday, June 21, 2015. Francis visited the long linen with the faded image of a bearded man, during his two-day pilgrimage to Turin. (L' Osservatore Romano/Pool Photo via AP)
Problems with Authenticating the Shroud of Turin
The Shroud of Turin is famous for claims that it is the burial shroud of Jesus, revealing his visage in dirt, grime, and blood as it was wrapped around him. The shroud has a long and storied history, supposedly taken from Judea around 33 AD, moved to Constantinople, then to Athens, and finally to a small town in France in the 14th century, when its existence was officially recorded. Carbon 14 dating done in the 1980s settled the question of authenticity for many scholars when it dated the fabric to the 13th-14th centuries AD. But what if Medieval clergy "fixed" an old, falling-apart garment with new material in the Middle Ages? These sorts of questions make many think that the shroud could indeed be real.
In a new article in Scientific Reports, lead author Gianni Barcaccia, a geneticist at the University of Padua in Italy, and his team report on their sequencing of DNA from the dust that they were allowed to vacuum from the shroud. They found plant DNA from various corners of the world, including spruce from Europe, clover from the Mediterranean, black locust trees from North America, and pear trees from East Asia.
Barcaccia and his team also isolated human mitochondrial DNA. The haplotypes they found also suggest that people from all over the world had access to the shroud, with genetic information consistent with residents of China and north Africa, in addition to Europe. But most of the mtDNA information comes from the Middle East and the area around the Caucasus Mountains, fitting with the idea that the shroud toured the Old World before ending up in France in the Middle Ages. Even more interesting is the finding of DNA consistent with people from India perhaps the material that made up the shroud was manufactured in India?
Of course, since the shroud has been recognized since the Middle Ages as a possible religious relic, it has been handled and moved about for centuries. There is unfortunately nothing in the new research to suggest a Medieval origin for the shroud and subsequent handling by people over the centuries is unreasonable. The question of whether the shroud is indeed a 1st century AD artifact or a Medieval artifact is not solved by the new analysis.
The question of the origin of the Shroud of Turin may yet be solved in our lifetimes, particularly as DNA analysis is getting more reliable, faster, less expensive, and less destructive. But I suspect that there will always be believers on both sides of the authentication argument, no matter what the results show.
Ancient DNA is obviously not the skeleton key that can unlock all the mysteries of history. yet. As these three stories from this week's news show, though, the rate at which DNA analyses are making headway in solving historical problems is staggering. As an archaeologist myself, I look forward to being able to apply these new techniques to my own research soon.
The 11,500-Year-Old Remains of a Baby Could Reveal How Humans First Came to the Americas
Ancient DNA extracted from the skull of a six-week-old baby girl whose 11,500-year-old remains were unearthed in a burial pit in central Alaska is helping scientists resolve long-standing controversies about how humans first populated the Americas.
Scientists said on Wednesday a study of her genome indicated there was just a single wave of migration into the Americas across a land bridge, now submerged, that spanned the Bering Strait and connected Siberia to Alaska during the Ice Age.
The infant — named “sunrise girl-child” (Xach‘itee‘aanenh T‘eede Gaay) using the local indigenous language — belonged to a previously unknown Native American population that descended from those intrepid migrants, the researchers added.
“The study provides the first direct genomic evidence that all Native American ancestry can be traced back to the same source population during the last Ice Age,” University of Alaska Fairbanks archaeologist Ben Potter said.
The remains of the infant — part of a hunter-gatherer culture that hunted bison, elk, hare, squirrels and birds and caught salmon — were unearthed in 2013 at a prehistoric encampment in Alaska’s Tanana River Valley about 50 miles (80 km) southeast of Fairbanks.
Our species first arose in Africa roughly 300,000 years ago, and later spread around the world. The researchers studied the baby’s genome and genetic data covering other populations to unravel how and when the Americas were first populated.
A single ancestral Native American group split from East Asians about 36,000 year ago and thousands of years later crossed the land bridge, they said. This founding group diverged into two lineages about 20,000 years ago.
The first lineage trekked south of the huge ice caps that covered much of North America between 20,000 and 15,000 years ago, spreading throughout North and South America and becoming the ancestors of today’s Native Americans.
The second was the newly identified population called Ancient Beringians who included the infant. They eventually disappeared, perhaps absorbed into another population that later inhabited Alaska.
Some scientists previously hypothesized about multiple migratory waves over the land bridge as recent as 14,000 years ago.
The girl was found alongside remains of an even-younger female infant, possibly a first cousin, whose genome the researchers could not sequence. Both were covered in red ochre and surrounded by decorated antler tools.
“Even the one that got sequenced was a huge challenge due to poor DNA preservation,” said Eske Willerslev, director of the University of Copenhagen’s Centre for GeoGenetics.
In the Bones of a Buried Child, Signs of a Massive Human Migration to the Americas
The girl was just six weeks old when she died. Her body was buried on a bed of antler points and red ocher, and she lay undisturbed for 11,500 years.
Archaeologists discovered her in an ancient burial pit in Alaska in 2010, and on Wednesday an international team of scientists reported they had retrieved the child’s genome from her remains. The second-oldest human genome ever found in North America, it sheds new light on how people — among them the ancestors of living Native Americans — first arrived in the Western Hemisphere.
The analysis, published in the journal Nature, shows that the child belonged to a hitherto unknown human lineage, a group that split off from other Native Americans just after — or perhaps just before — they arrived in North America.
“It’s the earliest branch in the Americas that we know of so far,” said Eske Willerslev of the University of Copenhagen, a co-author of the new study. As far as he and other scientists can tell, these early settlers endured for thousands of years before disappearing.
The study strongly supports the idea that the Americas were settled by migrants from Siberia, and experts hailed the genetic evidence as a milestone. “There has never been any ancient Native American DNA like it before,” said David Reich, a geneticist at Harvard Medical School who was not involved in the study.
The girl’s remains were unearthed at the Upward Sun River archaeological site in the Tanana River Valley in central Alaska. Ben A. Potter, an archaeologist at the University of Alaska, discovered the site in 2006.
It was apparently home to short-lived settlements that appeared and disappeared over thousands of years. Every now and then, people arrived to build tent-like structures, fish for salmon, and hunt for hare and other small game.
In 2010, Dr. Potter and his colleagues discovered human bones at Upward Sun River. Atop a hearth dating back 11,500 years were the cremated bones of a 3-year-old child. Digging into the hearth itself, archaeologists discovered the remains of two infants.
The two infants were given names: the baby girl is Xach’itee’aanenh T’eede Gaay (“sunrise girl-child,” in Middle Tanana, the dialect of the local community), and the remains of the other infant, or perhaps a fetus, is Yełkaanenh T’eede Gaay (“dawn twilight girl-child”).
The Healy Lake Village Council and the Tanana Chiefs Conference agreed to let scientists search the remains for genetic material. Eventually, they discovered mitochondrial DNA, which is passed only from mother to child, suggesting each had different mothers. Moreover, each infant had a type of mitochondrial DNA found also in living Native Americans.
That finding prompted Dr. Potter and his colleagues to begin a more ambitious search. They began collaborating with Dr. Willerslev, whose team of geneticists has built an impressive record of recovering DNA from ancient Native American bones.
Among them are the 12,700-year-old Anzick Child, the oldest genome ever found in the Americas, and the Kennewick Man, an 8,500-year-old skeleton discovered in a riverbank in Washington State. Questions over his lineage provoked a decade-long legal dispute between scientists, Native American tribes and the Army Corps of Engineers.
Living Native Americans descend from two major ancestral groups. The northern branch includes a number of communities in Canada, such as the Athabascans, along with some tribes in the United States like the Navajo and Apache.
The southern branch includes the other tribes in the United States, as well as all indigenous people in Central America and South America. Both the Anzick Child and Kennewick Man belonged to the southern branch, Dr. Willerslev and his colleagues have found.
So he was eager to see how the people of Upward Sun River might be related. But the remains found there represented a huge scientific challenge.
The search for DNA in the cremated bones ended in failure, and Dr. Willerslev and his colleagues managed to retrieve only fragments from the remains of Yełkaanenh T’eede Gaay, the youngest of the infants.
But the researchers had better luck with Xach’itee’aanenh T’eede Gaay. Eventually, they managed to put together an accurate reconstruction of her entire genome. To analyze it, Dr. Willerslev and Dr. Potter collaborated with a number of geneticists and anthropologists.
Xach’itee’aanenh T’eede Gaay, they discovered, was more closely related to living Native Americans than to any other living people or to DNA extracted from other extinct lineages. But she belonged to neither the northern or southern branch of Native Americans.
Instead, Xach’itee’aanenh T’eede Gaay was part of a previously unknown population that diverged genetically from the ancestors of Native Americans about 20,000 years ago, Dr. Willerslev and his colleagues concluded. They now call these people Ancient Beringians.
Beringia refers to Alaska and the eastern tip of Siberia, and to the land bridge that joined them during the last ice age. Appearing and disappearing over the eons, it has long been suspected as the route that humans took from Asia to the Western Hemisphere.
There has been little archaeological evidence, however, perhaps because early coastal settlements were submerged by rising seas. Thanks to her unique position in the Native American family tree, Xach’itee’aanenh T’eede Gaay has given scientists a clear idea how this enormous step in human history may have happened.
Her ancestors — and those of all Native Americans — started out in Asia and share a distant ancestry with Chinese people. In the new study, the scientists estimate those two lineages split about 36,000 years ago.
The population that would give rise to Native Americans originated somewhere in northeast Siberia, Dr. Willerslev believes. Archaeological evidence suggests they may have hunted for woolly rhino and other big game that ranged over the grasslands.
“It wasn’t such a bad place as we kind of imagine it or as we see it today,” he said. In fact, Siberia appears to have attracted a lot of genetically distinct peoples, and they interbred widely until about 25,000 years ago, the researchers determined.
About a third of living Native American DNA can be traced to a vanished people known as the ancient north Eurasians, known only from a genome recovered from the 24,000-year-old skeleton of a boy.
But the flow of genes from other Asian populations dried up about 25,000 years ago, and the ancestors of Native Americans became genetically isolated. About 20,000 years ago, the new analysis finds, these people began dividing into genetically distinct groups.
First to split off were the Ancient Beringians, the people from whom Xach’itee’aanenh T’eede Gaay descended. About 4,000 years later, the scientists estimate, the northern and southern branches of the Native American tree split.
According to Ripan Malhi, an anthropologist at the University of Illinois and a co-author of the new study, these genetic results support a theory of human migration called the Beringian Standstill model.
Based on previous genetic studies, Dr. Malhi has argued that the ancestors of Native Americans did not rush across Beringia and disperse across the Americas. Instead, they lingered there for thousands of years, their genes acquiring increasingly distinctive variations.
But while the new study concludes early Native Americans were isolated for thousands of years, as Dr. Malhi had predicted, it doesn’t pinpoint where.
“The genetics aren’t giving us locations, with the exception of a few anchor points,” said Dr. Potter.
Indeed, while the co-authors of the new study agree on the genetic findings, they disagree on the events that led to them.
“Most likely, people were in Alaska by 20,000 years ago, at least,” said Dr. Willerslev. He speculated that the northern and southern branches split afterward, about 15,700 years ago as the ancestors of Native Americans expanded out of Alaska, settling on land exposed by retreating glaciers.
Dr. Potter, however, argues that the lineage that led to Native Americans started splitting into three main branches while still in Siberia, long before reaching Alaska.
Pointing to the lack of archaeological sites in Beringia from 20,000 years ago, he believes it was too difficult for people to move there from Asia at that time. “That split took place in Asia somewhere — somewhere not in America,” Dr. Potter said.
If he is right, the mysterious earliest settlers of this hemisphere didn’t arrive in a single migration. Instead, the Ancient Beringians and the ancestors of the tribes we know today took separate journeys. “Even if there was a single founding population, there were two migrations,” he said.
But these scenarios all depend on timing estimated from changes in DNA, which “can be very sensitive to errors in the data,” Dr. Reich cautioned. More tests are required to be confident that the Ancient Beringians actually split from other Native Americans 20,000 years ago, he said.
And while the new study reveals the existence of the Ancient Beringians, it doesn’t tell scientists much about their ultimate fate.
But knives and other tools found at the Upward Sun River site belong to a tradition, called the Denali Complex, that endured until at least 7,000 years ago. The people who made those tools elsewhere in central Alaska may have been Ancient Beringians.
If so, they survived for nearly 13,000 years after splitting from the ancestors of other Native Americans. “The archaeology fits with them lasting for quite long,” said Dr. Potter.
The Native Americans who today live around the Upward Sun River site belong to the northern branch of the genetic family. The new study indicates that their ancestors returned north at some point to Alaska, perhaps replacing or absorbing the Ancient Beringians.
If the latter, and if geneticists are able to sequence more DNA from northern branch tribes, then they may stumble across living proof of an ancient North American people that no one knew existed.
“My answer to the question, ‘What happened to the Ancient Beringians?’ is: ‘We don’t know,’” said Dr. Potter. “And I like that answer.”
Baby skeletons hint at death rituals 11,500 years ago
Washington (AFP) - A pair of baby skeletons in Alaska are more than 11,500 years old, and offer new hints about the death rituals of early people in North America, researchers said Monday.
The bodies "represent the earliest known human remains from the North American subarctic," said the study in the Proceedings of the National Academy of Sciences, a peer-reviewed US journal.
The infants were found buried 15 inches (40 centimeters) beneath another child's cremated remains, in a circular pit that also held spear points with decorated antler shafts.
An analysis of bones and teeth at the Upward Sun River site in central Alaska revealed that one died shortly after birth and the other was a late-term fetus, researchers from the University of Alaska, Fairbanks and Liverpool John Moores University said.
The infants might have been related, and radiocarbon dating shows they were buried at about the same time as the cremated remains of the three-year-old child above them.
Researchers also found the remains of salmon-like fish and ground squirrels in the burial pit, suggesting that the site was occupied by hunter-gatherers between June and August, when food should have been plentiful.
It is unclear what caused their deaths, but researchers said the discovery of three burials in a group of mobile foragers suggests that food shortages could have been to blame.
"The deaths occurred during the summer, a time period when regional resource abundance and diversity was high and nutritional stress should be low, suggesting higher levels of mortality than may be expected give our current understanding" of survival strategies of the period, the study said.
The burials, found beneath a residential structure, also point to the possibility that people may have stayed in one place longer than previously believed.
Since little is known about death rituals in early humans, and they left behind no written language, researchers must cobble together clues based on what they can observe.
"The presence of hafted points may reflect the importance of hunting implements in the burial ceremony and with the population as whole," the study said.
The hunting weapons were found along with the infant skeletons -- first discovered by archeologists in 2013 -- and might have been added as part of the burial ceremony, researchers said.
"Taken collectively, these burials and cremation reflect complex behaviors related to death among the early inhabitants of North America," said Ben Potter, a researcher at the University of Alaska, Fairbanks.
Adaptable and persistent
The far north was one of the last places on Earth to be populated by modern humans, a species that evolved in Africa. And there is much to be learned by examining how our species migrated and then adapted along the way to survive and thrive in vastly different ecosystems — particularly in the north, where this group of ancient Beringians persisted from 12,000 to 6,000 years ago, weathering dramatic environmental shifts along the way, such as climate change, large extinctions of animal species and the emergence of evergreen forests, Potter told Live Science.
And the Beringians managed to do it without significantly changing their technology, centered on a unique type of stone tool called a microblade, he said. This tool was commonly seen in ancient hunter-gatherer societies in Asia but was not found anywhere else in North or South America, Potter said.
"Understanding the adaptive strategies that made that possible — the innovations, the social organization, how people cooperated and how they made their tools — is really a profound way to understand our species," Potter said.