Scientists Make A Discovery, Unlock Secrets About Ancient Human DNA
In the 1860s, Swiss chemist Friedrich Miescher discovered human DNA. This revelation helped scientists unlock secrets about our ancient ancestors. Even in 2018, researchers were making new discoveries. This particular excavation revealed several ancient secrets, including a previously unknown group of ancient humans. Read all about their discoveries here.
Two 11,500-Year-Old Skeletons
In 2018, archaeologists unearthed the skeletons of two Native American infants. Both were 11,500 years old and part of the same family.
These were not normal skeletons. They were well-preserved enough to inform scientists about early humans. In fact, they provide information about the first humans to ever visit North America.
Researchers Traveled To A Remote Area In Alaska
In the early 2000s, anthropology professor Ben Potter began working in Upward Sun River, Alaska. This forested area is 50 miles from Fairbanks and can only be reached by helicopter.
Despite the difficult terrain, Potter had good reason for excavating there. That part of Alaska was originally connected to Europe and Africa.
What Is Beringia?
When Pangea began breaking up, some strips of land still connected the continents. The earliest known humans were born in Africa, but they migrated across the world.
Beringia was the bridge that connected Siberia and Alaska. Many archaeologists believe that the first North American humans came from that bridge, over 34,000 years ago. However, this was just a theory.
The Beringian Standstill Hypothesis
Although many historians believe that early humans crossed Beringia, they do not know who did so. One theory, called the Beringian standstill hypothesis, attempts to answer this.
The hypothesis says that the "Ancient Beringians" lived on Beringia in isolation due to the ice and harsh climate. If this is true, the Beringians might be the sole ancestors of all Native Americans, according to archaeologist Jennifer Raff.
In Fact, Natives Still Live Near Upward Sun River
The name "Upward Sun River" is a translation from the Athabascan Xaasaa Na', the language of the Native Americans who still live in Alaska. It is also part of their territory.
Potter collaborated with the Natives for his excavations. Usually, they are very protective of their burial grounds; however, they understood the importance of Potter's work and offered to help him.
The First Discovery: A Three-Year-Old Child
In 2010, Potter and other researchers from the University of Alaska searched Upward Sun River. They discovered the cremated remains of a three-year-old child.
At 11,500 years old, this discovery was exceptionally rare. Unfortunately, the skeleton was not preserved enough to extract DNA from. Scientists could not even figure out the gender.
Despite The Letdown, Potter Didn't Give Up
Despite their limited success, Potter and his team did not give up. They continued to excavate in that area for eight more years.
Then, Potter and his colleagues, José Víctor Moreno Mayar and Lasse Vinner, found their big break. They unearthed a burial site in an area of Alaska that was around 15,000 years old.
Finally, They Found The Skeletons Of Two Infants
There, Potter and his team discovered two infant skeletons. One seemed to be a stillborn; the other was between six and 12 weeks old.
Like the three-year-old, the two seemed to have been cremated, as their remains rested on a fire pit. However, these remains were much more preserved and easier to identify.
The Burial Ground Was Well-Preserved
The two infants were buried beneath multiple items and covered in red ochre. This ochre, which was likely part of the funeral process, further preserved the skeletons.
The babies were also buried beneath a mixture of sand and soil. This high-acidity mixture is ideal for conservation. Clearly, the people who buried them loved them dearly.
Who Were The Two Girls?
DNA testing revealed that both infants were girls and that they were both related, possibly first cousins. The stillborn died at 30 weeks old, having never gotten the chance to live.
The local Native community named the girls Xach'itee’aanenh T’eede Gaay" (Sunrise Girl-Child) and "Yełkaanenh T’eede Gaay” (Dawn Twilight Girl-Child).
Other Items Were In The Grave, Too
This gravesite was clearly important to the mourners. Archaeologists discovered many other items in the grave, such as antler and spear points.
Both girls were buried together in a joint funeral. However, Sunrise Girl (the six-week-old infant) seemed to be better preserved and served as the basis for most of the DNA results.
What, Exactly, Were The Researchers Studying?
To examine the DNA, geneticists had to dig into the mitochondria. Science students remember the mitochondria as "the powerhouse of the cell" because, without it, cells die.
Every cell in the body contains DNA, and the mitochondria is responsible for running cells. Hence, the scientists need undamaged cells to examine--which is easier said than done.
Here's Why They Couldn't Study The Three-Year-Old
Old bones are not guaranteed to have live cells. If scientists want to examine DNA, they need a thick enough bone that is decently preserved.
Usually, researchers test the petrous bone, which is at the base of the skull. Because the three-year-old's bones were too damaged, researchers could not test the DNA. But with the two infants, they could.
What Came From The DNA Tests?
The first round of DNA tests, performed at the University of Alaska, revealed the ethnicity of Sunrise Girl. According to the results, she was closely related to Native Americans, but in a distinct way.
Scientists believe that her DNA is far older than any previously tested remains. In other words, she is a previously unknown genetic population of Native Americans.
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 back as 34,000. Eske Willerslev, the study's co-author and professor at the University of Copenhagen, says that they are the oldest known Native Americans to date.
"It changes our understanding of the timing of events that formed the genetics of Native Americans," Willerslev told CNN Health.
They Might Be Ancient Beringians
Sunrise Girl's DNA lends credence to the Beringian standstill hypothesis. Scientists believe that she might be an Ancient Beringian that experts had only theorized about beforehand.
"We think the explanation for this pattern, the one that requires the least movement, was 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's skull. Geneticists expected the second infant to have similar DNA. But surprisingly, she didn't.
Dawn Twilight Girl the stillborn, was examined at the University of Copenhagen, Denmark. She had an entirely different maternal lineage compared to her first cousin, and the lineages were not related.
Researchers Say There Were Two Branches Of Native Americans
Geneticists have separated Native Americans into two branches: Northern and Southern. The Northern group came from East Asia and likely inhabited North America, including Alaska and Canada.
At some point, the group split and the Southern Native Americans migrated to South America. They all descended from the Ancient Beringians, but the separation created variations in their DNA.
The Two Infants Had Different Ethnicities
In simpler terms, DNA tests indication that both girls belonged to two separate groups. Sunrise Girl belonged to the Ancient Beringias, while Dawn Twilight Girl came from another ethnicity, one more closely related to the Northern Native Americans.
This begets the question: how did these two groups of people end up in the same place at the same time?
However, Sunrise Girl Belonged To A Mysterious Third Group
Surprisingly, 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 East Asia 36,000 years ago. By 20,000 years ago, this group split. But if they split, why were these two infants buried together?
All Groups Split Off From One
In the study, archaeologists hypothesized that the two groups stuck together at least once--hence why the girls were related. They proposed two possibilities for this.
The Beringians might have split before crossing the bridge, only to reunite later. Or, the Beringians might have separated after crossing. Potter prefers the latter theory.
Perhaps They Split Before Beringia
Potter has a theory for how these two groups came together. During an interview with The Atlantic, he suggested that both groups independently crossed Beringia. Perhaps they traveled on different paths at separate times.
Usually, this theory would seem a bit far-fetched. But there is some evidence to back it up.
Support For Potter's Theory
In 2017, archaeologists examined the Bluefish Caves in Canada's Yukon Territory. According to a study on these caves, scientists found evidence of human-cut markings that were 24,000 years old.
If this is accurate, as Raff believes it is, then humans had crossed Beringia at least 24,000 years ago. That was over a decade before the two girls were born.
Still, There Are Many Unanswered Questions
Although 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 how rare these findings are, it is unlikely that these questions will be answered soon. And to make things more complicated, not all experts are on board with Potter's theories.
Some Experts Argued Against Potter's Conclusions
The main argument against this finding is just that: It's a single finding. Dennis O'Rourke, a geneticist and archaeologist, says that the one sample is not enough evidence to study the entire human population.
"We could know something about the extent of diversity in this early Beringian population with greater certainty if we had multiple genomes," O'Rourke told The Smithsonian Magazine.
However, These Findings Are Exceptionally Rare
But finding more than one sample is easier said than done. "It's hard to impress upon you how rare they are," Potter told The Atlantic.
According to co-researcher Willerslev, before this finding, scientists only had modern-day Alaskans and Siberians to study this genome. Without more samples, nobody will know where the Beringians came from.
Plus, Upward River Is Too Young For Ancient Humans
Despite the age of Upward River's burial grounds, archaeologist Brian T. Wygal claims that it is too young to understand early humans.
"The earliest proven trace of human activity in eastern Beringia dates to around 14.1-thousand-years-ago," Wygal explained, "making the Upward Sun River site nearly 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 released--which is in the scientific journal Nature--many have asked what happened to the Beringians. "We don't know," Potter told CNN.
Again, this question needs more evidence to answer. However, Potter plans to take DNA samples from the neighboring residents. Since scientists know what Beringian DNA looks like, they can determine if the gene still exists in Natives
What Were The Beringians Like?
Research has revealed a snapshot of the Beringian's life. According to Potter, they were expert hunters, eating bison, elk, rabbits, squirrels, and birds.
They likely hunted through organized parties. Potter also found evidence of "salmon exploitation" dating back 6,000 years, meaning that the Beringians likely fished and traded as well.
They Might Have Evolved Into The Modern Native Americans
Potter suggested that the Beringian gene might have assimilated into the indigenous peoples of Alaska. This is a natural consequence of evolution.
"It is possible that incoming Athabaskan ancestors, who are widespread throughout the region today, replaced or absorbed the Ancient Beringians inhabiting that area," Potter claimed. If that is true, many people might have Beringian blood and not even know it.
The Life-Threatening Diagnosis
In 2015, specialists diagnosed Chris Long with acute myeloid leukemia and myelodysplastic syndrome. But to Chris, those scientific terms translated to blood cancer. The father of two had abnormal tumor growth in his bone marrow, which infected his blood cells.
Those who have acute myeloid leukemia (AML) have a 24% chance of survival. The only treatment is to combine chemotherapy with a bone marrow transplant. While Chris considered his options, he understood that his future seemed bleak.
What Is A Bone Marrow Transplant?
During a bone marrow transplant, cancerous bone marrow is replaced with healthy marrow. Because bone marrow creates red and white blood cells, patients require an operation before their blood becomes too unhealthy.
Before Chris could receive the transplant, he had to undergo chemo to destroy the harmful cells. Then, he had to find a donor whose cells would not attack his body. Doing so was difficult, but fortunately, there are plenty of donors around the world.
Finding The Right Donor Is Harder Than It Sounds
However, finding a bone marrow donor is more complicated than finding a blood donor. To find a match, doctors examine donors' human leukocyte antigen (HLA). HLA is a protein that the immune system uses to know which cells are yours and which are not.
Each person has six different HLA markers. Doctors can pinpoint your HLA through a DNA test by swabbing the inside of your cheek. If the six markers line up, the donor's cells will not be "foreign" to the patient's immune system.
An Unusual Bargain
Fortunately, Chris found his donor quickly--an anonymous man from Germany. At the time, Chris worked as an information technology employee at the Washoe County sheriff's department in Reno, Nevada. They were a world apart.
Chris's sad diagnosis spread around his office. When the news reached them, forensic scientists of Washoe County took an interest in his case. They offered Chris an unusual opportunity that would challenge the scientific community only a couple of years later.
Can Your DNA Change?
Renee Romero, who led the crime lab at Washoe County, heard about Chris's situation through a colleague. The situation raised a question that Renee had been mulling over: would a bone marrow transplant change Chris's DNA?
Renee spoke to Chris about the opportunity to partake in an experiment. "We need to swab the heck out of you before you have this procedure to see how this DNA takes over your body," she remembered telling him.
A Human Guinea Pig
After hearing Renee's proposal, Chris agreed. He welcomed the distraction from his fatal diagnosis and his difficult path to recovery. During the conversation, he reportedly told Renee, "I don't even know if I will live."
Regardless, Chris began the joint experiment. Acting as a human guinea pig, Chris allowed the scientists to take samples of his DNA before he underwent surgery. The scientists would continue to monitor Chris's DNA throughout his remission and recovery.
Results Came Faster Than Expected
After his bone marrow transplant, Chris spent four years in remission. But Renee and her crime lab colleagues monitored him throughout his journey. Four months in, they analyzed Chris's blood. His German donor's DNA had replaced the genetic code in his blood.
The scientists also swabbed Chris's cheek, lip, and tongue. The DNA in these areas was replaced by the donor's as well. The DNA swapping was already accelerating faster than the forensic scientists had expected.
How Chris Transformed Into Another Person
The forensic scientists tracked Chris's DNA samples over four years. Within months, swabs of his arms, legs, body, and face had been replaced by his donor's DNA. Oddly, these findings fluctuated throughout the study. Some swabs contained both Chris's and his donor's DNA.
An even more surprising find was that Chris's semen had its DNA replaced. By the end of the four years, every area of his body had new DNA except for his chest and head hair.
The Shock Of A Lifetime
These findings baffled the forensic scientists at the Washoe County sheriff's office. No one expected Chris's DNA to be entirely overtaken by his donor. As criminalist Darby Steinmetz said, "We were kind of shocked that Chris was no longer present at all."
Chris was also shocked about the findings--but not to the point of despair. He told the New York Times, "I thought it was pretty incredible that I can disappear and someone else can appear."
He Is A Real-Life Chimera
So what happened to Chris? The bone marrow transplant had made Chris a chimera--the scientific term for people with two sets of DNA. The term stems from the monster in Greek mythology that was a hybrid of three animals.
Before Chris's study, forensic scientists knew that specific medical procedures cause chimerism. But they never researched where the donor's DNA replaced the patient's in the body. The fact that 99% of Chris's DNA had changed raised questions among the medical community.
This Has Been Studied Before
Chimerism from bone marrow transplants has been researched before. In 2004, research in Bone Marrow Transplantation reported that marrow transplants replace at least some of the patient's blood DNA. Even blood transplants temporarily replace DNA in the patient's blood.
However, these studies have only analyzed DNA changes in blood. Before the study on Chris, scientists have not tested how a patient's DNA changes in the rest of their body. In this sense, his case defied all expectations.
Will Chris Remain The Same Person?
The implications of Chris's case reached scientists far beyond Nevada. One nagging question was: would Chris remain the same person with someone else's DNA? Dr. Andrew Rezvani, the blood and marrow transplant professional at Stanford University, says yes.
"Their brain and their personality should remain the same," he told the Independent. He added that, if Chris's donor were female, it would not convert him to the female sex. "It doesn't matter," Dr. Rezvani stated simply.
For The Doctors, This Isn't An Issue
Although medical doctors understand the DNA change, they don't see it as an issue. As long as the transplant is successful, the change does not create any medical problems. The patient's medical history and mind do not change. So what's the issue?
For Renee and her colleagues, the DNA change does matter. As forensic scientists, they viewed Chris's case from the perspective of combating crime, and they knew that the DNA change could mean life or death for some.
...But It Could Throw Off Criminal Investigations
For forensic scientists, Chris's DNA change uncovered a new host of problems. When criminal investigators hunt down criminals, they rely on DNA swabs to lead to one person. What will happen if the DNA links to two people, one in Nevada and one ten years younger in Germany?
According to Brittney Chilton, a criminalist of the forensic science division, says that this DNA change could mislead investigators. It could result in someone being falsely accused of a crime they didn't do.
This Mix-Up Has Happened Before
In 2004, criminal investigators in Alaska thought they had caught a criminal when they uploaded a DNA sample to a database. There was just one problem: the man was in jail at the time of the crime. But DNA samples are flawless, right?
It turned out that the criminal's brother had received a bone marrow transplant. He was convicted, and a year later, crime detection scientist Abirami Chidambaram presented the case in 2005. It's the exact dilemma that Chilton was talking about.
But That's Not The Only Problem
According to Chilton, chimeras create another issue for the medical community. In 2008, research scholar Yongbin Eom tried to identify a victim of a car accident in Seoul, South Korea. His DNA showed that he was female--but his body was male.
It turned out that the victim received a bone marrow donation from his daughter. Chimeras have two sets of DNA: their original DNA and their donor's DNA. This may prevent medical investigators from properly identifying a body.
How Have Scientists Not Caught This Before?
Every year, thousands of people receive bone marrow transplants. The surgery is commonly recommended for patients with leukemia, sickle cell anemia, and lymphoma. Then how did this dilemma not surface before? Here's the thing: it has.
Bone marrow transfusions have interrupted criminal investigations before. Renee's study was the first in-depth research to explore DNA changes from a scientific perspective. The team presented Chris's case at the international forensic science conference in September of 2019.
Chimeras May Be Common (And In Trouble)
Studies suggest that chimerism may occur in 21% of triplets and 8% of twins. But these results don't explain how common the condition may be. If these chimera news stories hadn't come out, many people wouldn't know that chimerism even exists.
Most people don't take a paternity test to make sure that they're related to their biological family. As a result, many people could be chimeras and never know it. It only becomes an issue when a person's life is on the line.
Parents Could Lose Their Children
In some instances, chimerism may separate families. In 2002, Lydia Fairchild applied for child support. But the DNA tests said that she wasn't related to her children. During the case, she became pregnant with her third child--and the child still exhibited different DNA while in the womb!
Even though a judge arranged for a witness to be present for her third child's birth, the courts held her DNA tests above her doctor's testimony. Luckily, she was diagnosed as a chimera; otherwise, she would have lost her children.
What About Their Offspring?
Long's case raised another question. If a patient's DNA changed, and they had a child, would they create someone else's child? Renee surveyed three bone marrow transplant specialists for the answer to this question.
Although the experts agreed that it is an intriguing question, they highly doubted that a child's DNA would change. "There shouldn't be any way for someone to father someone else's child," reported Dr. Rezvani. After all, a donor's blood cells should not create new sperm cells.
Could Chris Have His Donor's Child?
If sperm isn't usually affected by transplants, why did Chris's change? According to Mehrdad Abedi, the doctor who treated Chris, his semen change likely resulted from his vasectomy. The fact that sperm couldn't move meant that their DNA would change.
If Chris hasn't had a vasectomy, would the same result occur? We don't know, and the scientists can't test this on Chris. DNA analyses of sperm have shown the donor's DNA instead of the patient's before. Time will tell.
Chimeras Can Occur Naturally
Human chimeras don't only result from bone marrow transplants. For instance, there's a case of a "vanishing twin," where one fraternal embryo dies early on. The remaining embryo absorbs the twin's DNA, resulting in two sets of DNA in the child.
During pregnancy, some women may retain some DNA from their baby. This phenomenon, called microchimerism, occurs in around 63% of women, even those over 94 years old. The New York Times says that microchimerism is "very common, if not universal."
But Identifying Chimeras Is Very Difficult
To make matters worse, it's not easy to tell if someone is a chimera. In 2015, parents discovered that their newborn's blood type and DNA did not match their parents'. They assumed that the clinic had used the wrong sperm.
Stanford geneticist Barry Starr recommended that the couple take a genetics test. Oddly, the test said that the father was the child's uncle. "Human chimerism is very common, but exquisitely difficult to identify, coming to light almost exclusively by accidents like this," biologist Charles Boklage told Buzzfeed News.
How This Study Impacted The Future
Chris's case has changed many peoples' opinions about DNA tests. Before, DNA tests were considered infallible in the courtroom. But the study suggests that common conditions may make DNA exams less foolproof than we assumed.
Chimeras have no issues in terms of health or medicine, but they create stumbling blocks for criminal investigators who rely on DNA tests to catch a perpetrator. With chimera cases coming to light, forensic scientists will have to redefine how they analyze DNA evidence.
Where Is Chris Now?
Chris Long recovered from his AML. He is now healthy and experiences no issues as a chimera (he is completely innocent!) He told the Independent that he planned a trip to Germany to thank his donor for saving his life.
Chris has not reported whether or not he'll continue working with the forensic scientists. However, Renee and her colleagues have suggested that they will continue to research the effects of chimerism -- specifically how it affects a patient's offspring.
