Scientists Uncover Secrets of Ancient Human DNA
In the 1860s, Swiss chemist Friedrich Miescher discovered human DNA, a revelation that helped scientists unlock secrets about our ancestors. This field of study continues to evolve, with new discoveries being made even in recent years. One such discovery in 2018 uncovered ancient secrets, including the existence of a previously unknown group of ancestral humans.
11,500-Year-Old Skeletons
In 2018, the exceptionally well-preserved skeletons of two 11,500-year-old Native American infants were found, and it was determined that they were part of the same family. These skeletons provided archaeologists with crucial insights into the first humans to inhabit North America.
The discovery was not an ordinary one. These skeletons were valuable keys to understanding the history of humanity and its evolution over time.
A Remote Expedition in Alaska
In the early 2000s, anthropology professor Ben Potter began his work at the Upward Sun River site in Alaska. This remote, forested area is located about 50 miles from Fairbanks and is only accessible by helicopter due to the rugged terrain.
Despite the difficulties, Potter had good reason to excavate there. The region of Alaska was originally connected to both Europe and Africa, which piqued his interest in studying human history and migration in that area.
What Was Beringia?
When the supercontinent Pangaea began to break apart, some land bridges still connected the continents. The first known humans originated in Africa, but over centuries, they migrated to other parts of the world.
Beringia was a land bridge that connected Siberia and Alaska during the last glacial period. Many archaeologists believe that the first humans to inhabit North America came via this land bridge more than 34,000 years ago, though at the time, this was just a theory.
The Beringian Standstill Hypothesis
While many historians believe that the first North American inhabitants crossed the Beringia land bridge, it was still unclear exactly who these early migrants were. A theory known as the Beringian Standstill hypothesis attempts to provide a possible answer.
According to this hypothesis, "ancient Beringians" lived in the Beringia area, isolated from the rest of the world by ice and extreme weather during the last glacial period. If this theory is correct, the Beringians may be the sole ancestors of all Native Americans, as suggested by archaeologist Jennifer Raff.
Natives Still Live Near the Upward Sun River
The name "Upward Sun River" is a translation of the native Athabascan language, Xaasaa Na', which is spoken by the indigenous people who still inhabit the region. The area is part of their ancestral territory.
Professor Potter collaborated with the local natives on his excavations. While indigenous communities are often protective of their archaeological sites, they understood the importance of Potter's work and offered their assistance.
The First Discovery: A Three-Year-Old Child
In 2010, Potter and other researchers from the University of Alaska were working at the Upward Sun River site when they found the cremated remains of a three-year-old child. At 11,500 years old, this was an exceptionally rare discovery.
Unfortunately, the skeleton was not well-enough preserved to allow for DNA extraction, and scientists were unable to even determine the child's sex.
Despite the disappointment, Potter did not give up. He and his team continued excavating the area for another eight years in search of more remains. It was then that Potter and his colleagues, José Víctor Moreno Mayar and Lasse Vinner, found a major opportunity. They discovered a burial site in an area of Alaska that was about 15,000 years old.
The Skeletons of Two Infants
In that region, Potter and his team made the discovery of two infant skeletons. One appeared to be stillborn, and the other was between six and twelve weeks old.
Like the three-year-old child, both skeletons seemed to have been cremated, as their remains were found in a fire pit. However, the remains of these two skeletons were better preserved and easier to identify.
The Well-Preserved Burial Site
The two infants were buried beneath several items and covered with red ochre, a reddish substance composed primarily of clay and iron minerals. This ochre, which was likely part of the burial process, further preserved the skeletons.
The infants were also buried under a mixture of sand and soil. This highly acidic mixture is ideal for preservation. It was clear that the people who buried them loved them very much.
Who Were the Two Girls?
DNA testing revealed that the two infants were female and related, most likely first cousins. The stillborn infant passed away at only 30 weeks of gestation and never had a chance to live.
The local indigenous community gave the girls the names "Xach'itee'aanenh T'eede Gaay" (Sunrise Girl) and "Yelkaanenh T'eede Gaay" (Dawn Twilight Girl). Other items were also found in the grave, such as horns and spearheads. Both girls were buried together in a single funeral. However, Sunrise Girl was better preserved and provided the basis for most of the DNA results.
What Exactly Were the Researchers Studying?
To examine the DNA, geneticists had to analyze the mitochondria. Mitochondria are remembered by students as "the powerhouses of the cell," as cells die without them.
All cells in the body contain DNA, and mitochondria are responsible for keeping the cells functioning. Therefore, scientists need undamaged cells to examine, which is easier said than done.
Why They Couldn't Study the Three-Year-Old
It is not guaranteed that old bones will have living cells. If scientists want to examine DNA, they need a thick, well-preserved bone.
Researchers typically test the petrous bone, which is at the base of the skull. Since the three-year-old's bones were too damaged, the researchers could not test for DNA. But with the two infants, they could.
What Did the DNA Tests Reveal?
The first round of DNA tests, conducted at the University of Alaska, revealed the ethnicity of the Sunrise Girl. According to the results, she was closely related to Native Americans, but in a distinct way.
Scientists believe that her DNA is much older than previously tested remains. In other words, she represents a genetic population of Native Americans that had not yet been identified.
They Revealed a New Ancient Human
This previously unknown DNA, which scientists dubbed USR1, dates back at least 20,000 years and possibly as far as 34,000 years ago. Eske Willerslev, a co-author of the study and a professor at the University of Copenhagen, says they are the most ancient known Native Americans to date.
"This changes our understanding of the timing of events that formed Native American genetics," Willerslev told CNN Health.
They May Be Ancient Beringians
The Sunrise Girl's DNA lends credibility to the Beringian Standstill hypothesis. Scientists believe that she may be an ancient Beringian, something that specialists had only theorized about before.
"We think the explanation for this pattern, the one that requires the least movement, is that Native Americans were somewhere in Beringia 20,000 years ago," explained Victor Moreno Mayar, another author of the study.
But the Two Girls Had Different DNA
The first DNA analysis was done on the six-week-old infant's skull. Geneticists expected the second infant to have similar DNA, but surprisingly, she did not.
The Dawn Twilight Girl, the stillborn infant, was examined at the University of Copenhagen in Denmark. She had an entirely different maternal lineage compared to her first cousin, and the lineages were not related.
Researchers Say There Were Two Native American Groups
Geneticists have separated Native Americans into two groups: Northern and Southern. The Northern group came from Eastern Asia and likely inhabited North America, including Alaska and Canada.
At some point, the group split and Southern Native Americans migrated into South America. They all descend from the Ancient Beringians, but the split created variations in their DNA.
The Two Children Had Different Ethnicities
Simply put, the DNA tests indicated that both girls belonged to two different groups. The Sunrise Girl belonged to the Ancient Beringians, while the Dawn Twilight Girl came from another ethnicity more closely related to northern North Americans.
This raises the question: How did these two groups of people end up in the same place at the same time?
However, the Sunrise Girl Belonged to a Third Mysterious Group
Surprisingly, the Sunrise Girl did not belong to either of these groups. This means that the ancient Beringians split into at least three groups, if not more.
With demographic modeling, scientists estimated that Native Americans left Eastern Asia 36,000 years ago. 20,000 years ago, this group split. But if they split, how were these two infants buried together?
All Groups Split from One
In the study, archaeologists hypothesized that the two groups were together at least once, which would explain why the girls were related. They proposed two possibilities for this.
One possibility is that the Beringians separated before they crossed the land bridge and then came back together again. The other is that they separated after the crossing. Potter prefers the latter theory.
Perhaps They Split Before Beringia
Potter has a theory as to how these two groups came together. During an interview with The Atlantic, he suggested that both groups crossed Beringia independently. Perhaps they traveled different paths at different times.
While this theory may seem a bit far-fetched, there is some evidence to support it.
Support for Potter's Theory
In 2017, archaeologists examined the Bluefish Caves in the Yukon territory of Canada. According to a study on these caves, scientists found evidence of man-made markings that were 24,000 years old.
If this is accurate, as Raff believes it is, then humans crossed Beringia at least 24,000 years ago. This was more than a decade before the two girls were born.
Still, There Are Many Unanswered Questions
While the discovery of the girls proved many hypotheses, it also raised several questions. What happened to the Beringians? How did they get to Siberia in the first place?
Given the rarity of these discoveries, it is unlikely that these questions will be answered anytime soon. And to make things more complicated, not all experts agree with Potter's theories.
Some Experts Argued Against Potter's Conclusions
The main argument against this discovery is simply this: it is a single finding. Dennis O'Rourke, a geneticist and archaeologist, states that a single sample is not sufficient evidence to study an entire human population.
"We could have a more accurate understanding of the diversity of this early Beringian population if we had multiple genomes," O'Rourke told The Smithsonian magazine.
Yet, These Findings Are Exceptionally Rare
Finding more than one sample is easier said than done. "It's hard to convey just how rare these are," Potter told The Atlantic.
According to co-researcher Willerslev, before this discovery, scientists only had the genomes of the current inhabitants of Alaska and Siberia to study. Without more samples, no one will know the origin of the Beringians.
Also, Upward River Is Too Young for Ancient Humans
Despite the age of the Upward River archaeological site, archaeologist Brian T. Wygal states that it is too young to understand the first humans.
"The oldest substantiated trace of human activity in eastern Beringia dates to about 14.1 thousand years ago," Wygal explained, "making the Upward Sun River site almost 3,000 years too young to be representative of the initial human colonization of the New World."
What Happened to the Beringians?
After Potter's study was released in the scientific journal Nature, many asked what happened to the Beringians. "We don't know," Potter told CNN.
Again, this question needs more evidence to be answered. However, Potter plans to collect DNA samples from nearby residents. Since scientists know what Beringian DNA looks like, they can determine if the gene still exists in the natives.
What Were the Beringians Like?
The research provided an overview of Beringian life. According to Potter, they were skilled hunters who fed on bison, elk, rabbits, squirrels, and birds. Hunting was likely performed in organized groups.
Additionally, evidence was found that they were exploiting salmon fishing around 6,000 years ago, suggesting that the Beringians also practiced fishing and possibly trade.
They May Have Evolved into Modern Native Americans
Potter suggested that the Beringian gene may have been assimilated by the indigenous peoples of Alaska. This is a natural consequence of evolution.
"It's possible that the Athabaskan ancestors, who are spread throughout the region today, either replaced or absorbed the ancient Beringians who inhabited that area," Potter said. If this is true, many people may have Beringian blood and not even know it.
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