A bulldozer gouges into the dirt of a dusty construction site near Mexico City. But as the machine makes light work of the plot, a curious object is spotted deep underground. There, jutting out from the upturned earth, is an enormous, fragile bone. And it’s not alone. Archeologists carefully unearth dozens, and eventually hundreds, more of the eerie relics. These aren’t your typical animal skeletons, though. No, these are the remains of a horde of gargantuan beasts, and they’re a truly fearsome find.
As well as being enormous, the bones are also exceptionally rare. And while this detail left many archeologists thrilled, the discovery of subterranean skeletons didn’t please every party with links to the Mexico City site. The Mexican authorities had hoped to construct a brand new airport on the plot by 2022, you see. But the excavation of the curious relics hampered the project’s progress.
Archeological work is a slow process, after all. Excavating the airport site took experts almost a year to complete. The land’s gruesome underground secret was first recognized in late 2019. And then experts went on to carefully exhume and catalog hundreds of vast, mysterious skeletons from that unlikely location.
But what were these strange creatures which had thrived in the Mexican landscape? And why did so many of these huge animals meet their fate on the outskirts of Mexico City? Well, the answers to these questions provide a fascinating glimpse into what sorts of fearsome beasts once roamed the region.
Of course, North America’s recent past has been dominated by human activity. Mexico City, for example, was founded by the Aztecs in the first half of the 14th century. And with such a lengthy and storied past, it’s perhaps unsurprising that the region has gifted archeologists so many remarkable artifacts from long ago. Yet the recent discoveries at the Santa Lucía airport site date back to long before advanced civilizations appeared in the Americas.
Thousands of years ago, the land where Mexico City now stands looked very different from how it does today. In place of the skyscrapers and parks that make up the modern metropolis sat a network of vast lakes – stretching out across the Valley of Mexico. Chief among these bodies of water was the huge Lake Texcoco, which covered more than 2,000 square miles.
Eventually, the Aztecs would choose an island in Lake Texcoco as the setting for Tenochtitlan – the settlement that would later become Mexico City. But for a long time, the region was home to a far wilder way of life. Early humans eked out a living on the huge lake’s shores long before the Aztecs arrived, after all. And they likely shared the land with an array of spectacular beasts.
Yes, huge creatures that weighed in at more than 100 pounds could be seen roaming the Mexican landscape many millennia ago. This was the time of the so-called megafauna, according to experts. And in North America, these huge species often took the form of oversized ancestors of the animals that we know and love today. So, could one of these ancient giants have left behind the bones that eventually turned up beneath Santa Lucía airport?
Might the skeletons have belonged to the ancient horses that emerged on the North American continent some 50 million years ago? Apparently, these creatures disappeared from the region around the 12th century B.C., though they survived in other parts of the world. Or perhaps the remains were those of something altogether more bizarre – such as the glyptodon.
Capable of growing over 10 feet in length, the glyptodon was essentially a giant version of the modern armadillo. The creature was so large, in fact, that its bones may be comparable to the ones recently discovered at Santa Lucía airport. And because the species once thrived in North America, its remains have been uncovered across the continent. So could this be the latest in a long line of finds?
Amazingly, glyptodons and ancient horses aren’t the only species that could have supplied the Santa Lucía airport site’s cache of bones. The remains could have also belonged to a dire wolf, which was a prehistoric North American carnivore that lived during the Late Pleistocene and Early Holocene eras. Or maybe they were the skeletons of its competitor, the saber-toothed cat.
It’s also possible that the warmer climate of what is now Mexico City tempted creatures such as the megalonyx – or ground sloth – back down south after their forays further north. Fossils belonging to these giant creatures have been recovered from modern-day Mexico, after all. Perhaps the skeletons at Santa Lucía airport were also left behind by these lumbering beasts?
But none of these guesses truly aligns with the mass of giant bones uncovered during the airport dig. So which mysterious creatures had perished on the site all those years ago? Well, thanks to earlier excavations elsewhere, archeologists already had some clues as to what they might find – ones that early humans had inadvertently left behind.
Humans are thought to have been present in the Valley of Mexico up to 12,000 years ago, you see. This means that they likely interacted with a number of the megafauna species that once inhabited the region. In fact, hunting is believed to have played a significant role in the decline of these giant creatures.
Interestingly, though, it wasn’t just their relationship with man that sealed the fate of these colossal beasts. Humans adapted as temperatures began to rise. But creatures such as the ground sloth and the saber-toothed cat did not. And one by one, the continent’s megafauna succumbed to extinction – leaving nothing but their great bones behind.
Many thousands of years later – in 2019 – archeologists began excavating the ground where the new Santa Lucía facility was to be built. Originally an Air Force base, the project was announced by the President of Mexico in the first half of 2019. Before that, the authorities had planned to build a new airport to the northeast of Mexico City, but a referendum had stalled work on that project.
The Santa Lucía site was selected as a suitable alternative, then, and work began on expanding the former base into a commercial airport. But as construction got underway, archeologists from the National Institute of Anthropology and History were keen to be involved. They had heard that some startling excavations were taking place at a dig site nearby, you see. So they wanted the chance to investigate the airport plot as well.
The nearby dig had taken place outside the town of Tultepec, which is some 12 miles from the Santa Lucía airport site. And in November 2019 the researchers responsible for the project announced some startling news. They had uncovered a pair of artificial pits seemingly dug by humans thousands of years ago. And evidence suggested that these structures had played a role in an innovative ancient hunting technique – and a successful one at that.
Amazingly, the researchers found no fewer than 14 skeletons inside the Tultepec pits – each belonging to the species known as the Columbian mammoth. The experts theorized that early humans had constructed the six-foot-deep traps so that the huge creatures could not escape. Primitive hunters may even have actively chased the animals towards their fate.
But what did the hunters do with these huge mammoths once they’d caught them? It’s believed that they butchered the creatures for their meat and bone. Altogether, it was a far more sophisticated approach than the primitive spear-hunting that many associate with this time. So were these early humans perhaps smarter than they have been given credit for?
Well, to determine whether the pit-hunting technique was simply a one-off, experts from the National Institute of Anthropology and History became involved in the Santa Lucía airport dig. And thanks to the recent Tultepec discovery, they knew what to look for. But would the ground reveal any more relics from a time when man lived shoulder-to-shoulder with giant beasts?
Fortunately, researchers did not have to wait long to find out the answer. Over a six-month period commencing in October 2019 they uncovered more than 50 mammoth skeletons and were due to excavate many more. National Institute of Anthropology and History archeologist Pedro Sánchez Nava told the Associated Press in May 2020, “There are too many, there are hundreds.”
Nava explained that over the course of those six months, the team had been unearthing the giant bones at a rate of around 10 skeletons a month. And at the time, they had predicted that this frequency could continue for many weeks to come. But the Santa Lucía airport dig eventually surpassed even those great expectations.
Yes, archeologists announced in September 2020 that at least 200 vast skeletons had been discovered at the site. Not only that, they believed that there were more waiting to be excavated. And with this revelation, Santa Lucía airport shattered the record for the most mammoth bones ever found at a single location.
According to experts, the bones date back some 10 or 20 millennia, to a time when much of the Valley of Mexico was covered in water. Alongside Texcoco, Lake Xaltocan was another of the interconnected bodies of water that covered the basin. And here, animals such as the mammoth found a hospitable home.
But what drew the megafauna to Lake Xaltocan? A rich habitat of reeds and grasses tempted beasts such as mammoths to feast by its shores. Experts believe that the creatures were capable of consuming over 300 pounds of these nutrients a day. As Nava explained to the Associated Press, “It was like paradise for them.”
The lake was clearly a popular spot, drawing the vast creatures from far and wide. And nowadays, so many mammoth skeletons are buried in the former lakebed that any digging by bulldozer there needs to be accompanied by an observer. Yes, spotters were enlisted to ensure that construction work at the Santa Lucía site didn’t accidentally damage any fragile bones.
The Santa Lucía airport site is worth protecting, it seems. Dubbed “mammoth central” by some archeologists, the dig could well provide some vital clues to how these creatures lived and what led to their extinction. But how did so many of them end up dying in the same location? According to researchers, they may have become trapped in the soft soil of the lakeshore.
At the moment, though, experts are unsure whether or not humans played a role in this gruesome fate. The mammoths may have found themselves stuck in the marshy ground after visiting the lake to feed. But did early hunters take advantage of the natural trap that was created by the lake?
Nava wouldn’t rule out the possibility that humans had been involved. “It’s possible [early hunters] may have chased [the mammoths] into the mud,” he told the Associated Press. “They had a very structured and organized division of labor.” In fact, archeologists have found several tools forged from the creatures’ bones close to the skeletons.
But the tools made of bone aren’t necessarily proof that humans utilized the natural trap of Lake Xaltocan to hunt mammoths. Alternatively, they may have butchered the creatures after they became stuck in the mud and died. Or the tools could have been crafted from the bones of animals killed elsewhere before being brought to the site.
Experts plan to carry out tests on the skeletons to see if they show any signs of human interference. Until this can be determined, though, they can only speculate about the relationship between mammoths and the early inhabitants of Lake Xaltocan. That said, the bones have still proved invaluable to scientists studying these ancient creatures.
Experts believe that the species known as the Columbian mammoth first appeared in North America around one million years ago. The creature’s ancestor – the steppe mammoth – had arrived in the region from Asia several millennia before. And for thousands of years, these giant beasts roamed the Valley of Mexico and feasted on the local vegetation.
According to scientists, these mammoths were capable of growing over 13 feet tall – around the same height as an adult female giraffe. And while similar species in Europe evolved thick, hairy coats to insulate them from the cold, their North American counterparts did not. Online news outlet Business Insider also notes that the Columbian mammoth likely had a lifespan similar to that of a modern human: between 70 and 80 years.
Although many people are familiar with the image of humans hunting mammoths, the two species likely only coexisted for a short period. The Columbian mammoth died out, of course. But the Paleoamericans who hunted the species eventually disappeared, too. So was man responsible for the great beast’s extinction? Or was something else at play?
Well, scientists hope that the Santa Lucía discovery might help to shed some light on the Columbian mammoth’s decline. Speaking to the Associated Press in September 2020, paleontologist Joaquin Arroyo Cabrales explained, “What caused these animals’ extinction, everywhere there is a debate, whether it was climate change or the presence of humans. I think in the end the decision will be that there was a synergy effect between climate change and human presence.”
And the Santa Lucía airport discovery has brought the world of science one step closer to solving that mystery. After all, it is rare to find such a large grouping of mammoth skeletons together in one place. Paleontologist Ashley Leger told the Associated Press in September 2020, “A very specific set of conditions that allow for a collection of remains in an area – but also be preserved as fossils – must be met. There needs to be a means for them to be buried rapidly and experience low oxygen levels.”
Mammoth graveyards such as this one are rare, but humans have been uncovering their giant bones for hundreds of years. In fact, even the Aztecs – who ruled from nearby Tenochtitlan – once stumbled across vast skeletons buried beneath the ground. Yet they could only guess at the creatures that had left them behind. According to Nava, they were so stumped by the remains that they concluded giant humans had once walked the Earth.
Interestingly, the Santa Lucía airport excavations may also reveal more about the role that mammoths played in the early human diet. Speaking to the Associated Press in May 2020, Nava explained, “They used to think [the eating of mammoth] was very [dictated by] chance – sporadic. In fact, it may have been part of their daily diet.”
But it wasn’t just mammoths discovered at the site in Mexico. No, researchers also uncovered other remains – including five horses and camels. And according to experts on site, there are still several excavations due to take place. So will Mexico City’s new airport have any more tricks up its sleeve? The facility is apparently on track to open in 2022, so archeologists may be up against the clock.
Of course, Santa Lucía airport isn’t the only burial site to have shed light on the history of North America. A plot at the Upward Sun River in central Alaska, for example, revealed something striking back in 2013: the remains of two infants. The pair of skeletons dated back around 11,500 years, meaning they were the remains of some of the earliest North American settlers. And as it turns out, those tiny bones held 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 provide the most startling discovery.
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. 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, 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.”