When Scientists Studied Infants’ Skeletons, They Discovered Ancient Secrets Locked Inside Their DNA
This article contains interesting insights that address two big questions: First, when did humans arrive in North America? And second, would the global climate, as the popular understanding maintains, be stable if humans weren’t using fossil fuels?
The date of human arrival on this continent is steadily being pushed back from the commonly-accepted date of about 12,000 years ago. As the authors write , “So those first human journeys into Alaska from Siberia likely happened more than 30,000 years ago. It seems, too, that those brave travelers may have stayed put on this land bridge for a long time. Then, roughly 15,000 years ago, the glaciers covering North America began to disintegrate. And it’s believed that this was the cue for humans to leave Beringia (the land bridge), eventually cross North America and spread to the south.”
Again quoting the authors, regarding climate change: “However, this land bridge (Beringia) disappeared around 12,500 years ago when the last glaciations came to an end and sea levels rose. And while many people refer to that glaciation as the last ice age, that is not strictly correct. In fact, we’re technically still in an ice age—albeit a warm one that geologists call the Quaternary. This period has lasted for nearly 2.6 million years, and it’s deemed an ice age because the poles have been frozen for all that time.”
A professor and his team are excavating a burial site at the Upward Sun River in central Alaska.
Then, as the group painstakingly remove soil, they come across something striking: the remains of two infants. In fact, since this site is around 11,500 years old, they’re looking at human skeletons from the earliest North American settlers. And as it turns out, these tiny bones hold a stunning secret about America’s past.
The two sets of remains – which were originally uncovered in 2013 – were later found to have come from a baby who died around six to 12 weeks after birth and an infant who looked to have been stillborn. It seems, too, that the children were buried together and that they may have once been female cousins. And the bones were only actually discovered following a previous development in 2010.
Yes, in that year anthropology professor Dr. Ben Potter and his team came across what was left of a three-year-old. These remains were located on top of a firepit, meaning the toddler was probably cremated after death. Then, years later, they found the other children lower down, and the unearthing of their bones would in turn would provide the most startling discovery.
You see, those two children – unlike the three-year-old – were well-preserved enough to allow for DNA analysis. What’s more, scientists were able to retrieve enough genetic material from one of the girls to reach some startling conclusions about how humans first arrived in North America. But before we find out more about what this means, let’s go back to the start of the story.
Potter had first found the ancient Upward Sun River (USR) site in 2006. This location is situated in the heavily forested lands of the Tanana River Valley, some 50 miles from the city of Fairbanks, Alaska. And the area is so remote that it can only be reached by helicopter.
Interestingly, the name of the site, Upward Sun River, is a translation from the Athabascan language – the local Native American tongue. And the First Nation people living nearby chose to give the two infants names from the Athabascan language, too. In fact, the researchers went out of their way to collaborate with the community during their excavations.
Yes, Potter worked to gain the trust of the natives. While in the past the First Nation people had been very protective of ancient remains, in this case they’d given their blessing for the academic to start his excavation. So, the Healy Lake Tribe called the site Xaasaa Na’, meaning Upward Sun River, with Potter happily accepting this name.
Meanwhile, the tribespeople named the younger of the two girls Yełkaanenh t’eede gaay, which translates as dawn twilight child-girl, and the elder Xach’itee’aanenh t’eede gaay, which means sunrise child-girl. It emerged, too, that the site where they had been discovered had likely once housed a settlement used by hunter-gatherers, whose food sources had seemingly included bison, squirrels and hares.
Yet previous research has rather intriguingly shown that most of these ancient sites, described as Paleo-Indian, were fairly transient camps. In other words, people tended to move on from them quite quickly. Conversely, though, Upward Sun River showed signs of permanence. You see, the location hosts remnants of residential buildings – the oldest of their kind to be found in Alaska. The area near the bodies also included specks of salmon and small animals. And this is unique, as temporary camps tended to be used by hunters searching for larger game such as elk and wooly mammoths.
But let’s return for a moment to the first child whose remains were found in 2010. Well, although teeth analysis showed that the infant was around three years old, the scientists were unable to determine its gender. Separately, it’s likely that the firepit where the body was cremated was used to cook food beforehand. And the evidence shows that the camp was probably deserted after the death and burial of the child.
Yet the two children buried beneath the firepit seem to have had much more elaborate interments than the infant who was cremated. For starters, they had been surrounded by various burial goods covered in red ochre. And the high level of preservation also came as a surprise to the experts. That’s because the remains were buried in sand and soil, which is a highly acidic mix and is not usually good for conservation.
Other items found within the grave included pieces of antler and spear points made from sharpened stone. And Potter has in fact theorized that the antler fragments – more precisely rods – could have been combined with stone to make projectiles. As he told Science magazine in 2014, “You can even see the whittling marks left on the edges of [the antlers].”
In any case, Potter was certain that the two infants were buried at the same time, as they had been laid side by side. And, ultimately, the researchers were able to determine their gender through the close analysis of their remains, as each had small bulges on their jaws and incisions on their pelvic bones.
So, it’s clear that the community to which the two infants belonged were concerned enough to give them a proper funeral. Indeed, the loss of two young children would no doubt have been a bitter blow to the families concerned. And since DNA evidence indicated that the two little girls were probably cousins, that must have especially been the case here.
Another key factor to consider is the rarity of these finds. That’s right: very few human remains that are this ancient have been discovered in Alaska before. And after coming across the USR site back in 2006, years of painstaking work had paid off for Potter, as he and his team finally unearthed what can only be described as archeological gold.
Yet the real value of these archaeological finds wasn’t just their age or scarcity. What was even more important was that these human remains were well enough preserved to be sources of DNA. And as a consequence, that meant they could potentially yield crucial information about the human journey into North America.
As we’ve mentioned, the scientists could not extract DNA traces from the remains of the three-year-old who’d been cremated. For the other two children, though, it was a completely different story. In fact, the bones of “sunrise child-girl” produced a particularly good DNA sample.
Additionally, the area where the two girls were found in the Tanana River Valley is of special interest to archeologists tracing the movement of humans into North America. The location is known as the ancient land of Beringia, and 11,500 years ago it was a land bridge that joined today’s Alaska with what is now Siberia.
However, this land bridge disappeared around 12,500 years ago when the last glaciations came to an end and sea levels rose. And while many people refer to that glaciation as the last ice age, that is not strictly correct. In fact, we’re technically still in an ice age – albeit a warm one that geologists call the Quaternary. This period has lasted for nearly 2.6 million years, and it’s deemed an ice age because the poles have been frozen for all that time.
Within the current ice age, then, there have been periods of glaciation – or extremely cold weather – when the ice on the poles has extended towards the equator. The last glaciation ended about 12,500 years ago after lasting for more than 100,000 years. And at its peak, possibly around 22,000 years ago, a two-mile-deep ice field lay over what is now New York City.
More importantly, though, one of the impacts of these huge ice sheets was a huge drop in global sea levels. Yes, so much water was locked up in the ice that the oceans were largely depleted. And this meant that land between Alaska and Siberia was exposed, which in turn allowed humans to cross from Asia into North America.
So those first human journeys into Alaska from Siberia likely happened more than 30,000 years ago. It seems, too, that those brave travelers may have stayed put on this land bridge for a long time. Then, roughly 15,000 years ago, the glaciers covering North America began to disintegrate. And it’s believed that this was the cue for humans to leave Beringia, eventually cross North America and spread to the south.
Of course, these pathways of human migration are complex, and scientists don’t necessarily have all the answers. While some believe that humans stopped off at Beringia for a long period, others think that successive waves of migrants crossed the land bridge and traveled southwards. Unfortunately, though, evidence is hard to come by, as Beringia is now under the sea.
The hypothesis on the successive waves of migration is supported by most contemporary Native Americans, who belong to five distinct genetic bands that specialists call A, B, C, D and X. But what’s known as the standstill theory says that this diversity wasn’t actually the result of different groups arriving from Siberia. Instead, it came from Beringia, where one wave of people stopped long enough to develop a diverse gene pool before migrating through the Americas.
Yet the discovery of the infants’ remains gave researchers hope that fresh insights could be made into these migration patterns. And now that Potter had uncovered those ancient remains, it was time to see what information they might yield. The next step, therefore, was DNA analysis.
So, the bones of the two children were handed over to a team of scientists headed by The University of Utah anthropologist Justin Tackney. This group were entrusted with the complex task of extracting genetic material from the remains. And what they were specifically hunting for was mitochondria.
Mitochondria are microscopic organelles that are classically known as “the powerhouses of the cell.” They’re responsible for transforming elements found within our food into energy. They also capture waste material and negate their harmful effects. In other words, mitochondria are essential building blocks of cellular life.
But from the point of view of a biological anthropologist such as Tackney, mitochondria have another specific and highly useful property. If researchers can extract DNA from the mitochondria in ancient bones, they can work out an individual’s maternal lineage. And, fortunately, scientists were able to do just that with the remains of the two girls.
Still, once the experts had undertaken that delicate process, they were in for an immediate surprise. Quite unexpectedly, you see, it turned out that these two children had completely different maternal lineages. Specifically, one came from a DNA subgroup known as C1b, while the other was from a subgroup called B2. That was startling given that the two infants had apparently died and been buried together.
Then another team of genetic specialists – this time in Denmark – performed more detailed analysis. In this case, the scientists concentrated on DNA material that had been extracted from the skull of the older infant, sunrise girl-child. She was the one who had died at between six and 12 weeks.
Rather incredibly, the Copenhagen researchers then compared sunrise girl-child’s DNA with genetic material from 167 separate global populations – both ancient and modern. And the conclusion was that there had likely been one single flight from Beringia going south into the Americas rather than a series of successive population movements. In other words, the findings lent credence to the “standstill model” of migration.
The results of these tests also showed that sunrise child-girl and dawn twilight child-girl had mothers who were from two distinctively different genetic groups. As mentioned earlier, these groups are known as C1b and B2, and while they are quite often found in Native Americans living today, they are absolutely unknown in people who inhabit modern Siberia. From this, the specialists inferred that genetic diversity must have arisen during a long period of human occupation in Beringia.
In 2018 scientist Miguel Vilar explained to National Geographic, “20 years ago, we thought the peopling of America seemed quite simple, but then it turns out to be more complicated than anyone thought.” John Hoffecker from the University of Colorado Boulder told the publication, however, that there was still “plenty” of debate to be had over the ancestral origins.
Even so, Potter’s team’s findings – which were published in January 2018 – have a direct bearing on the human migration story of the Americas. This is because the work supports the idea that there was a prolonged period of standstill – during which those who had left Siberia settled either at the Beringia land bridge or near it. And the researchers have come up with a new name for these people: the Ancient Beringians.
In addition, Potter and his colleagues now believe that the infants’ different genetic groups developed in Beringia rather than arriving with migrants from Siberia. It appears, too, that the C1b subgroup first appeared about 12,800 years ago, with the B2 group emerging approximately 800 years later. And these timescales support the idea that there was a lengthy period of settlement in Beringia before it was subsequently lost to rising sea levels.
Speaking to Science magazine in 2015, Justin Tackney explained, “The people at [Upward Sun River] existed only a few thousand years after the initial expansion into the Americas occurred, so they might represent a residual Beringian group.” And he added that, owing to Beringia now being underwater, “this is the closest we might ever get to seeing what the Beringians were like genetically.”
Another geneticist, the University of Florida’s Connie Mulligan, has also lent her support to the standstill theory. She told Science, “They [the Ancient Beringians] settled in Beringia for thousands of years.” Mulligan continued, “Genetic variants specific to the New World evolved. When the ice sheets began melting about 15,000 years ago, [these people] crossed into the New World as the first settlers.”
Indeed, the discovery of the two infants has seemingly opened up a whole new chapter on America’s early settlers. In a 2018 press release by the University of Alaska Fairbanks, Potter is quoted as saying, “We didn’t know this population existed. These data also provide the first direct evidence of the initial founding Native American population, which sheds new light on how these early populations were migrating and settling throughout North America.”
Potter continued, “It would be difficult to overstate the importance of this newly revealed people to our understanding of how ancient populations came to inhabit the Americas. This new information will allow us [to have] a more accurate picture of Native American prehistory. It is markedly more complex than we thought.”
And while speaking to National Geographic, the professor concluded, “Knowing about the Beringians really informs us as to how complex the process of human migration and adaptation was. It prompts the scientist in all of us to ask better questions and to be in awe of our capacity as a species to come into such a harsh area and be very successful.”
Of course, this isn’t the first time that experts have used DNA to make a revolutionary new discovery about the migration of early humans. You see, while experts have long thought that humankind had originated in Africa, new genetic evidence now seems to prove otherwise.
A massive lake glistens beneath the sun, cutting a clear expanse across an otherwise lush wetland, some 200,000 years ago. Here, a new species – Homo sapiens – has gathered. These modern humans have evolved from their Neanderthal ancestors, and humankind has at last started its reign. Yet scientists have just now pinpointed the surprising place where it all began.
In fact, geneticist Vanessa Hayes of the Garvan Institute of Medical Research in Sydney led a study that used specific scientific data to pinpoint this exact verdant locale. In particular, Hayes and her expert team had to rely on mitochondrial DNA, which they had gathered from the cells of 1,217 samples. This battery-shaped genetic material passes from mothers to their children, so the researchers naturally had to find a population with a maternal line that stretched far into the past.
With the right DNA information gathered and analyzed, then, the research team highlighted a general area of origin. And after that came further archaeological and geological research that in turn helped Hayes and co to find something spectacular: evidence of a massive, ancient lake that broke down into wetlands. Its lush greenery was the backdrop for the first humans to walk the Earth, they say, and its modern-day location may just surprise you.
Experts have, of course, long believed that humankind traced all the way back to the African continent. But mapping evolutions and migrations has been a difficult task, to say the least. It was about seven million years ago when human beings began to evolve, after all, splitting off from primates such as the chimpanzee and the bonobo.
So it’s virtually impossible to find every link between humans and primates, since scientists simply don’t have enough fossil records to achieve this. In fact, entire species may have come and gone without leaving a trace for experts to uncover today. That’s why, in some cases, there are only bits and pieces of evidence to work with.
Yet the picture of humankind’s ancestral roots becomes clearer as scientists move nearer to the present day. They know, for example, that Neanderthals roamed Europe and even trekked into Siberia and Central Asia – although not as far as Africa. But while this population may have paved the way for modern humans, they did not actually originate the species.
Instead, it would be the evolution of Homo heidelbergensis and Homo erectus that gave way to Homo sapiens. And these new humans presented a variety of slight differences that separated them from the likes of the Neanderthal population who roamed the continent before them. For one, Homo sapiens took on a more slender build than the stockier Neanderthals up north.
In addition, modern humans mastered the art of making tools in a way that Neanderthals hadn’t. The African contingent styled their weapons to have sleek, elongated blades, for example. They also fashioned their weapons into more sophisticated throwing spears – which made their hunting more effective. The Neanderthals, by contrast, wielded clunkier weapons that had been chiseled from large stones.
But the fact that both the Homo sapien and Neanderthal populations had similar lifestyles did initially confound modern-day experts. As a result, then, scientists formulated two main theories about how and where humankind had developed. Some believed in what’s called the multi-regional hypothesis. This states that human ancestors spread across the globe – thus allowing modern humans to evolve in a handful of different places worldwide.
Then there is a single-origin concept known as the Out-Of-Africa theory. As the name suggests, this idea purports that modern humans grew and evolved on the continent for millennia before migrating to other areas of the Earth. And during the 1980s, scientists seemed to have gathered what appeared to be a clear confirmation of the Out-Of-Africa theory.
This was due to DNA testing. In fact, DNA testing completely revolutionized science in a number of ways. In terms of determining humankind’s ancestral roots, though, scientists could – using these tools – analyze the genetic information of modern populations. From there, they traced multiple subjects’ lineages back into the distant past, and these mappings seemingly always led researchers to one place of origin: Africa.
In these original studies, too, experts relied on mitochondrial DNA when tracing their subjects’ ancestral lineages. This part of the genetic code comes from people’s mothers. In addition, this section of DNA will present mutations more readily than others. So it’s therefore easier to follow how mutations have passed from mothers to children for generations.
In fact, in repeatedly tracing this mitochondrial DNA back all the way to the cradle of civilization, experts realized that one woman’s genetic code has been carried through to everyone on Earth today. She’s known to scientists as “Eve” – although she’s not the same as the biblical figure. She is not considered as the first ever human woman on Earth, after all.
Rather, this Eve lived when the entire human population consisted of a mere 10,000 people. So Eve was neither the only – nor the oldest – of our ancient predecessors. She just happened to have an unbroken line of daughters who passed her mitochondrial DNA onto their baby girls and down through the ages right through to the present day.
In short, Eve is regarded as humankind’s “most recent common ancestor,” according to Smithsonian magazine. A 2008 DNA analysis confirmed, too, that she is the only woman of that time to have an unbroken lineage of daughters. And the scientists behind the study also concluded that Eve had originated in Africa – more specifically, the eastern area of the continent.
Eve’s DNA therefore seemed to reveal the start of humankind’s story. Yet the experts had lots of other questions. If the species originated in Africa, for instance, how did they spread out to other continents? And why are such a disproportionate number of fossils from Europe? To answer these queries, then, the researchers combined the same DNA evidence with archaeological finds.
And all of this information pointed to major migrations that started between 60,000 and 80,000 years ago. At that time, then, modern humans seemingly left their African origins for Asia. By about 45,000 years ago, though, they had already moved into Australia, Indonesia and Papua New Guinea, too. Then, 5,000 years after that, bands would leave Africa for Europe.
Humans who journeyed from Africa to Europe likely took one of two pathways to get north. Some would have traced the Mediterranean coast to get onto the continent, while others probably passed through Turkey and along the Danube. Their insurgence also pushed Neanderthals into a few mountainous areas – until the species disappeared altogether about 25,000 years ago.