The two children’s teeth were found deep within the frosty muck. Each was smaller than a dime.
Russian archaeologist Vladimir Pitulko discovered them a dozen years ago along the bank of the Yana River in northern Siberia. He didn’t realize it at the time, but he’d uncovered the oldest human remains ever to be found in the Arctic. Preserved within their enamel-shelled cores is ancient DNA. The information encoded in that genetic material can enrich our understanding of humanity’s prehistoric past.
And scientists have recently learned how to decode it.
The 31,000-year-old teeth and their DNA were part of a larger study, co-authored by an anthropologist at Southern Methodist University, that analyzed 34 ancient human remains scattered across the Siberian tundra. The findings, published this summer in the journal Nature, provided insights into the earliest human voyage through arctic Siberia during the last Ice Age. The people would eventually populate the Americas, giving rise to modern Native Americans.
We’ve thought for centuries that Native American ancestors entered Siberia from northeast Asia. Then the last Ice Age reached its lowest temperatures around 20,000 years ago. The early humans eventually split into separate groups and shuffled south — likely thinking, “Where the hell can I survive in the midst of this Ice Age in Siberia?” said David Meltzer, the SMU anthropology professor and co-author of the study.
Scientists previously assumed that these early humans likely traveled as a single group. The new findings, however, shoo that simple idea off the stage and present strong evidence for a more complex story.
The authors found there were several major migrations into northern Siberia during the last Ice Age, not just one. This created a “fairly complicated ancestral tree” for Native Americans, Meltzer said.
Scientists need close scans of ancient DNA to parse out how migrating, prehistoric populations mixed and mingled. Time has unfortunately degraded that DNA into tiny bits, creating an intractable jigsaw puzzle. At least, it used to be.
Thanks to the Human Genome Project’s completion in 2003, scientists got an answer key for the human DNA puzzle — a fully sequenced human genome. With a reference genome in hand, the study’s authors solved key parts of the puzzle by using advanced biotechniques collectively called “next-generation DNA sequencing” developed just over the past couple of decades.
The teeth are a perfect demonstration of how much more you learn if you can make sense of tattered, ancient DNA. The teeth’s genetic material revealed that they belonged to members of a previously unknown human group, which the authors call Ancient Northern Siberians.
They were the first people to populate Siberia, “a group of people before Europeans and Asians diversified from each other,” said Eske Willerslev, a professor at the University of Copenhagen Center for Geogenetics and a co-author of the study. “I can’t even describe to you what they would look like.”
Another major find presented in the study was a 10,000-year-old skull discovered along the Kolyma River in Siberia. The authors showed that the Kolyma individual was a Native American ancestor — the closest connection to modern Native Americans ever discovered outside the Americas.
Scientists first pieced together an ancient human genome in 2010, right in Willerslev’s lab. That accomplishment gave a steroid boost to ancient genetics research. “Ancient DNA is exploding,” Meltzer said. “There are labs starting all over the planet.”
Professor Anne Stone at Arizona State University runs one such lab. Stone, an anthropological geneticist who was not involved in the study, lauded the latest research as “done very well.” From the teeth, the authors obtained genomic data from people who lived before the last Ice Age reached its coldest point. She emphasized it’s the first time researchers have gotten data like this.
It’s also the only time. Stone pointed out that “the story could change slightly” if more remains are found and analyzed. “Their genome is the one telling us the story, but it’s part of a larger story.” She wasn’t that perturbed by the limited data. After all, human remains this old are nearly impossible to come by in the Arctic. And the field of ancient DNA is so new.
In fact, Pitulko uncovered the teeth along Yana’s riverbank in the mid-2000s, years before ancient DNA research blossomed.
Pitulko and his team have been excavating that riverbank for over a decade, digging out a site almost the size of a football field. After years of “hard, muddy work,” Pitulko has found thousands of artifacts. But no ancient human remains besides those teeth. They were a fascinating find, but without being able to extract insight from their DNA, they weren’t particularly useful.
The aged teeth sat for years until Willerslev realized his lab could make use of the DNA within them. Unlike the muddy mess that Pitulko works in, Willerslev analyzed the ancient DNA in a sterile room where every person is treated as a possible contaminant. Rightly so. Even a stray hair or skin flake has enough modern human DNA to overwhelm the meager, ancient samples.
Accordingly, the scientists are garbed in white onesies, gloves, booties and hairnets. They will even write their names on their face masks, so you know who’s working underneath.
Much of the Yana site has yet to be excavated. The researchers may find more human remains that improve our understanding. But time is limited. Climate change was freezing Siberian soils tens of thousands of years ago, but today’s climate is warming them rapidly. The site’s frozen ground has been thawing and collapsing into the river. The riverbank’s been retreating by dozens of feet every year.
“Now all the area we excavated is under water — including the area which produced the teeth,” Pitulko said. The authors expect years of work left in Yana, but Pitulko emphasizes that they must “dig before it gets washed out.”
“This is actually a battle,” he said. If not recovered, undiscovered remains of our ancestors may collapse into the river, their ancient DNA puzzles remaining forever unsolved.
Jordan Wilkerson reports on science for The Dallas Morning News as part of a fellowship with the American Association for the Advancement of Science.