In an underwater cave in Mexico’s Yucatán Peninsula, researchers wearing full scuba gear are about to make a startling discovery. Through the gloom, two divers called Vicente Fito and Ivan Hernandez have found some ancient bones. And these remains may challenge what we know about the early colonizers of the American continent.
We’ll learn more about the significance of these old bones a little later, but let’s first learn about the area in which they were found. The state of Quintana Roo isn’t just home to ancient underwater caves, it also houses the popular Xlpor Park. And as part of their stay, adventurers can actually visit the subterranean caverns.
Despite being very much submerged these days, the Quintana Roo cave system wasn’t always underwater. In fact, during the Last Glacial Maximum period around 19,000 years ago, the sea level around the Yucatan Peninsula was around 330 feet lower. And this means that the caves were easily accessible to land-bound creatures – including humans.
And while adventurers dive in the caves, many may be blissfully unaware of the ancient history beneath them. That’s where Instituto de la Prehistoria de América AC director Jerónimo Avilés and his team come in. The group is based at the Xplor Park, where they retrieve and analyze discoveries from the underwater caverns.
The discoveries made in the Quintana Roo caves cover an amazing array of fossilized wonders. But some of the most significant finds here are the ancient human remains. And Avilés’ field laboratory – which operates in conjunction with the Museo del Desierto in Coahuila – is where the items are first analyzed before being sent to other labs across Mexico.
The fossils are dehumidified in order to stop what is known as fungal colonization – something common in tropical climates. The laboratory is also home to 3D-printed versions of the remains discovered in the caves, and this allows researchers to study humans who haven’t seen the light of day for thousands of years.
These remains, though, can be difficult to come by. For example, to reach the bones that we mentioned earlier, the experts had to jump into a freshwater pool and make their way through nearly 3,000 feet of dark underwater tunnels. Avilés told The Yucatan Times in February 2020, “It was quite a challenge because of the remoteness of the site, [it takes up to 70 minutes of] swimming at a good pace [to get there].”
And once the team had arrived in the cave where these particular bones were found – known as Chan Hol – they didn’t have much room to maneuver. Avilés explained, “Only two people can fit in the cave. Besides, it’s a very low place – barely [three feet] from floor to ceiling.” Researchers then had to spend hours combing the area for archeological treasures. But the tribulations didn’t end there.
That lack of room in the cave presented its own special challenge for the experts. Avilés told The Yucatan Times, “… The visibility is quickly ruined. It only takes four breaths and the water, the clearest you’ve ever seen, [gets muddied].” Clearly, searching for ancient relics in Mexico is not for the faint of heart.
But the experts’ hard work in the caves has proven its weight in gold. According to The Scientist, ten skeletons have been found in the wider cave network. And the discoveries have fueled an important archeological debate about what happened to some of the first people who arrived on the American continent.
On a wider note, there has long been a debate as to when and how humans colonized the Americas. The first theory – known as the “interior route” – posits that people crossed the so-called Bering Land Bridge between northeast Siberia and North America. From there, they then made their way down through the continent.
Many believe that humans followed herds of animals east from Siberia on the aforementioned land bridge, which had been made usable due to falling sea levels during a period called the Last Glacial Maximum. Nevertheless, the theory goes that these people eventually crossed into modern-day Alaska. But this isn’t the only possible way that humans could have colonized the Americas.
The other suggestion as to how humans arrived on the continent is known as the “coastal route.” It argues that inhabitants of northeast Siberia traveled via Russia’s Kurile Island chain by boat – passing the archipelagos on the coast of Alaska and British Columbia. They eventually sailed down to Central and South America – surviving on fish along the way.
However the first settlers arrived, experts do appear to agree on a couple of things. Firstly, those explorers did indeed most likely come from the aforementioned part of Siberia. And secondly, they probably arrived in the Americas anywhere from 15,000 to 40,000 years ago.
Crucially, Mark Hubbe of the Ohio State University explained to The Scientist magazine that there are less than 20 skeletons from the aforementioned period in the entire Northern Hemisphere. Quintana Roo is also the only place where experts have found more than one human from the same time period and region.
The team dating the remains of the bones that we mentioned earlier was led by Wolfgang Stinnesbeck, who is a paleontologist at the University of Heidelberg in Germany. He reported to the Nature journal that his colleagues discovered evidence of an animal called a peccary – a mammal related to pigs – in the caves. Evidence of man-made fires were found there, too.
Experts found their first skeleton at the cave site back in the early 1990s. Now known as Eva de Naharón, she is believed to be more than 13,000 years old. Another of the ten skeletons discovered here was spotted in 2012 by divers in the Chan Hol cave. However, the majority of the remains were sadly stolen before anyone could fully analyze them.
Thankfully, researchers were able to examine bone pieces left behind following the theft and ascertain their age. It’s then that they were able to confirm that the skeleton – known as Chan Hol II – shared a similar age to Eva de Naharón. For reference, the two skeletons are among the oldest human remains to ever be discovered in the Americas.
And there’s a particular ailment which appears to bind many of these early humans together. Stinnesbeck and his team reported that another skeleton they studied from the cave site had tooth decay. But they weren’t alone; dental issues such as tooth loss, abscesses and cavities appear to have been common among this population, according to Discover Magazine.
Experts believe that these early humans lived on a diet that largely consisted of sweet fruits, honey and root vegetables. Of course, many of these foods can lead to tooth decay. And the dental issues were apparently a particular issue among the female population.
In addition, the kind of damage caused by eating grains and meat simply wasn’t present among people found in the Quintana Roo caves. This backs up the theory of a sugar-rich diet among the residents, and it suggests that they probably didn’t do a lot of hunting. Another set of remains, however, gave us clues to a very different facet of the lives of these people.
Experts are of the opinion that a number of the individuals found in the caves had actually fallen to their deaths. Others, however, appear far more deliberately placed, as if they were laid to rest. And one of these individuals – known as Young Man of Chan Hol – was found in lying in a strange position in 2006.
The skeleton is believed to be around 10,000 years old and was found lying on his side. His arms were straight, following the line of his body, and his legs were bent. Such a position is, for researchers, evidence that he may have been laid to rest there. So could the caves have been a burial site for these ancient people? Well, the discovery of another carefully arranged set of bones certainly adds weight to that theory.
In February 2020 experts led by Wolfgang Stinnesbeck from Heidelberg University revealed the discovery of an extraordinary set of remains. Though the female bones had been disturbed by the water in places, they too appeared to have been deliberately placed. Most of the body was found on a limestone slab and she was lying down. Furthermore, researchers believe that the woman had lived in the area around 10,000 years ago and that she was a Paleoindian – the group who it’s thought were the first to colonize the Americas.
In addition to the evidence of a deliberate burial, the newly discovered remains held many revelations – including one that could change our understanding of early populations in the Americas. The woman – who was around 30 years old when she passed – was named Ixchel by the researchers and she paints a picture of a life lived in pain.
Ixchel’s teeth showed the tell-tale signs of a sugar-rich diet. But her tooth decay had taken a turn for the worse. Left unchecked, the condition had caused an abscess which grew deep into her jaw. This had led to the loss of several teeth and it would have caused a huge amount of pain. But this ancient woman’s story doesn’t end there.
Interestingly, Ixchel’s skull had suffered three separate head injuries. At some point, the woman had endured two blows to the back of her head with something sharp. She’d survived both attacks, it appears, as new bone had grown to cover the wounds. As for the third strike, that was caused by a different kind of weapon.
According to the research – which was led by Stinnesbeck and published in PLOS ONE in February 2020 – Ixchel’s third injury had come from a blunt instrument striking the left side of her head. However, bone regrowth shows that she also survived this blow. And aside from signs of arthritis in her other bones, no one really knows what led to her death. The 10,000-year old skull, though, showed signs of an altogether different kind of attack.
While we may never know how or why Ixchel received those head wounds, her skull showed signs of something that researchers could, at least, partially explain. They wrote, “In addition to traumas, the skull of the… female exhibits irregular dents and crater-like deformations on the posterior parietal and occipital bones of the cranium.”
The scarring on Ixchel’s skull was likely caused by a bacterial infection, Stinnesbeck and his team believe. Apparently, research points to the condition being a treponemal disease related to syphilis.
This revelatory diagnosis means that Ixchel’s remains are the oldest ever discovery of a human displaying signs of a so-called treponemal disease. Not only that, but she predates other skulls with the condition by a whopping 8,000 years. This find could help shed light on the origins of these bacterial infections and indicate when humans first encountered them. And still, there was yet more to come.
Despite the wealth of information gleaned from Ixchel, she still had more surprises in store. While DNA extraction is typically used to determine the genetic origins of ancient remains, that wasn’t possible in this case. The bones had been exposed to freshwater and saltwater – destroying the collagen needed to conduct those tests.
Researchers, then, had to use different methods to try and determine Ixchel’s ancestry. One of those techniques involved analyzing the size and shape of her skull. The team used the cranial index – a measure of how round a head is – and the results left them shocked.
Ixchel’s skull is what’s known as mesocephalic – or more spherical in shape. But that’s not the same form as other craniums found in North America from the same period. Those are dolicocephalic, which means they are narrower and longer. Even remains found in other parts of Mexico older than 9,000 years fit in to the latter category. But Ixchel isn’t alone; the Quintana Roo cave skulls more generally are believed to be mesocephalic.
Stinnesbeck and co believe that the existence of Ixchel and the other Quintana Roo skeletons points to an astonishing possibility. The remains suggest that two distinct human populations lived in Mexico around 12,000 years ago. The differences in these other humans are thought to come either from their geographical background or quick adaptations which took place to the local environment. And the facial differences even among each other varies significantly.
The research, then, posits that these early settlers of the American continent were much more diverse than we ever imagined. And further studies of other skulls found in the cave complex suggest that the theories of migration from a single location may need rethinking somewhat.
Avilés and a group of experts led by Ohio State University’s Mark Hubbe compared four copies of the skulls discovered in Mexico with those from modern populations across the world. And their findings – which were published in January 2020 in PLOS ONE – lent further support to the idea that these ancient humans were a diverse bunch.
The latter study suggested that these ancient craniums actually share many features with modern populations around the planet. For instance, Eva de Naharón is very similar to an Arctic North American human. And she wasn’t the only individual to share a striking likeness with modern-day beings from other countries.
Another skull known as El Pit I apparently shares a likeness to a modern European sample, while the cranium of Las Palmas resembles Native American and Asian people. Hubbe and his colleagues did, however, caution that the several of the samples were considerably fragmented and the comparison was built on only a few landmarks. Furthermore, a fourth skull known as Muknal didn’t have much of a similarity to any other modern specimen.
María Ávila-Arcos – who is an evolutionary geneticist at the National Autonomous University of Mexico – talked to The Scientist about the significance of Hubbe’s findings. She said that “the population was genetically very homogeneous,” adding, “maybe there was more diversity than what we anticipated, and that’s reflected in differences in the skull morphology.”
Stinnesbeck, meanwhile, believes that this community of people in Quintana Roo may have been particularly unique. He told the publication, “It’s quite likely that this group was ecologically isolated.” Indeed, he and Avilés have discovered a plethora of unique animals which inhabited this part of Mexico during the period in which these skeletons lived. Stinnesbeck concluded, “[It’s] like a continental Galapagos.”