When Did Humans First Inhabit the Americas?

What happens when an archaeological site is so extraordinary, that it threatens to eclipse everything we knew about history up to that point? Some discoveries are just too hard to fully grasp, and that makes us question their accuracy.  Hueyatlaco in Mexico is one such archaeological site, forcing us to reconsider the timeframe of human habitation in the Americas. By a lot. The finds presented at Hueyatlaco are still a matter of heated debate amongst scholars today, but one thing is certain - there are still many unanswered questions which need to be explored. 

The Hueyatlaco and the Enigmatic Traces of Early Man

The Valsequillo Basin is located near the city of Puebla, in Mexico. Situated in the central part of the country, this basin has been the focus of much interest for geologists, archaeologists and the scientific world as a whole. This interest was sparked due to the presence of numerous megafaunal remains and evidence of very early human habitation. Megafauna, as we know, is the term commonly used for large animals that roamed the landscapes of the Pleistocene, such as  mammoths, woolly rhinoceroses, and cave lions. However, although rich in important discoveries, the site has always been the cause of much  controversy, simply because some of the theories surrounding it are very hard to fully grasp.

It has been proposed that the landscapes of the Early Pleistocene period were characterized by many deep lakes, and that this basin might once have been one such lake. However, no direct proof for this ever surfaced and dating has proven quite difficult for scholars. Nevertheless, the area is of immense geological interest due to it being dominated by the stratovolcanoes  Popocatépetl and La  Malinche, and its location in the Trans-Mexican Volcanic Belt. As such, this is a site with a time-worn history, which also helps shed some light on early human habitation of the region, because  geology and archaeology often go hand in hand.

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Some of the first excavations at Hueyatlaco were carried out in 1961, when professor Cynthia Irwin-Williams conducted an extensive dig at the site. Even before she arrived, the region was known as a place rich in animal fossils, which sparked the interest of scholars. Irwin-Williams was soon joined by other prominent persons of the U.S. Geological Survey, notably Virginia Steen-McIntyre, who was responsible for publicizing the find and the magnificent discoveries it entailed. Due to the vast numbers of animal fossils, it was commonly believed that this site was a kill site, where ancient humans butchered the animals they  hunted.

The countless animal remains were located in fluviatile deposits commonly known as Valsequillo gravels, which were often plain and exposed in the high cliff sides of the Valsequillo Reservoir. Some of the ancient animal fossils found included  bison, camel, dire wolf, peccary, short-faced bear,  sloth, horse, tapir,  mammoth, saber-toothed cat, mastodon, glyptodon, four-horned antelope, and several other species. But the really important finds were made in 1962, when Irwin-Williams discovered both animal  bones and stone tools, together,  in situ.  The subsequent struggle to positively identify the age of these remains led to much controversy.

During excavations at Hueyatlaco in Mexico, Cynthia Irwin-Williams discovered animal bones, fossils and stone tools together. The dating of these remains has created unending controversy. ( Erica Guilane-Nachez  / Adobe Stock)

A Conundrum of Man’s Earliest Origins

The tools that were discovered included some very crude and primitive implements, but also tools that were much more sophisticated, with double edges and detailed flaking construction. These tools were diverse and included quite elaborate projectile points, many of which were made from non-local materials. This was a clear proof that Hueyatlaco was used by various groups of people for a long period of time. Either way, these findings were quickly pushing back the previously believed timeline of human habitation in South America, which caused conflicts in the scientific world.

Very early on in the excavations, attempts were made to discredit the work done at Hueyatlaco, and some turned out to be blatant attacks on the work. Someone seemingly had a problem with the idea that South America was inhabited so much earlier than was commonly believed. In 1967, Jose Lorenzo, a member of the Mexican  Instituto Nacional de Antropologia e Historia,  came forth with a controversial claim that the artifacts discovered were deliberately planted at the site, in a way that made it difficult to know whether they were actually discovered. This gossip was seemingly unmerited and looked a lot like an attempt to disrupt the crew from making further claims at the site.

What is more, the suspicious activities did not stop here. Irwin-Williams did make a startling discovery of  mammoth bone fragments that were carved with intricate images, depicting various megafauna animals such as serpents and saber-toothed cats. Similar carved images have been discovered all over the world, and are associated with early man. However, these carved bones disappeared under puzzling circumstances, as if someone didn’t want them to reach the public eye. Photographs of the carvings survive.

Virginia Steen-Mcintyre working on the Hueyatlaco site in the mid-1960s. ( The Pleistocene Coalition )

Stigmatized Because of the Truth Because of Hueyatlaco Results

By 1969, Irwin-Williams sought support in the scientific community, and gained support from three renowned scholars who visited the site of the excavations and confirmed that everything was being conducted in a professional manner. During that same year, the team published their first scientific paper that detailed the excavations and the importance of the site. And that importance was  the age . 

Various methods for dating the finds were utilized, many of which were revolutionary for the time. The usual  radiocarbon dating  indicated that the remains were roughly 35,000 years old. However, dating by uranium suggested the remains to be far older, roughly 260,000 years old. At the time, these results were considered an anomaly, especially due to the fact that general science proposed a general time of 16,000 years before present for the settling of the  Americas.

Some suggested that the strata (or geological layers) were eroded by ancient waterways, and that might have mixed up the specimens, and causing such differing results. By 1973, scientists returned to Hueyatlaco, hoping to conduct new excavations and attempt to once more examine the layers and to resolve the oddities of dating the finds. However, their research concluded that the layers  were not  eroded and that specimens were not mixed up. 

What is more, this new team managed to analyze volcanic ash from the site and apply the revolutionary zircon fission track dating method. Through this geochemistry approach, they determined that the volcanic ash - discovered in the same layer as the tools - was roughly between 370,000 and 240,000 years old. This confirmed the extremely old age of human habitation at the site, and further deepened the enigma that was Hueyatlaco.

In time, plenty of friction arose between the team members, as they could not agree on the age, the direction in which the excavation was heading, or the accuracy of the dating methods. Uranium dating was extremely new at the time, and its reliability not well known, while the fission track dating method had a substantial margin of error. In time, the excavation team was separated by their views. 

Irwin-Williams believed that the probable age was 20,000 years before present, although that view in itself was considered controversial by many. On the other hand, Harold Malde and Virginia Steen-McIntyre, other team leaders, firmly believed the original dating of 200,000 years before present - which was so revolutionary that it was hard to comprehend. Some suggested that the 20,000 year theory by Irwin-Williams was “puzzling” and almost a deliberate tactic to discredit the find. This was believed mainly because no evidence for that age was found in the excavations at all.

The excavations at Hueyatlaco unearthed stone tools, some of which were very crude and primitive implements, but others that were far more sophisticated. ( Ancient Origins )

A Tearing of the Scientific Community

Irwin-Williams never went forward to solidify her claims. In fact, she never published a report on the site whatsoever, which led to questions on the honesty of her claims. On the other hand, the other part of the team firmly believed in their 200,000 year theory, and were not willing to drop it. In 1981, this faction made up of Malde, Fryxell, and Steen-McIntyre published an extensive scientific paper in the  Journal of Quaternary Research , providing a detailed insight and evidence for the extremely old dating of human habitation at the site. 

In their paper, they provided the results from four different dating tests: the fission track, the uranium-thorium test, the study of mineral weathering to determine age, and the tephra hydration tests. All of these tests confirmed the age of the remains to be roughly 250,000 years old which confirmed their theories. To that end, the authors wrote in their paper:

"The evidence outlined here consistently indicates that the Hueyatlaco site is about 250,000 years old. We who have worked on geological aspects of the Valsequillo area are painfully aware that so great an age poses an archaeological dilemma [...] In our view, the results reported here widen the window of time in which serious investigation of the age of Man in the New World would be warranted. We continue to cast a critical eye on all the data, including our own."

This was an educated, accurate response that acknowledged that such a radical claim  did seem odd, but was not entirely impossible. The story of Hueyatlaco continued to look like a deliberate attempt to discredit these finds or hide them under the carpet. The evidence was there: early humans could have inhabited the so-called New World, the Americas, far earlier than was commonly believed. 

But seemingly, someone did not want that truth to be accepted. To that end, Irwin-Williams, who was at odds with the rest of the team, raised objections to several aspects of the published paper, seemingly continuing her attacks on the finds. The team were confident and quickly refuted her attempts to discredit their work.

Controversial Results at Hueyatlaco Silenced from the Shadows

Further secrets were soon revealed. Virginia Steen-McIntyre was at one point fired from her job due to her claims, and she also revealed that some of the original team members were harassed, their careers were threatened, and they were proclaimed incompetent - all because of their involvement in the project. So, we need to wonder, why did these findings cause so much enmity from mainstream science? Sure, to some, the claims of such an old age might seem radical and hard to believe. But rather than simply disagreeing with the claims, mainstream scholars went to great lengths to attack, harass, and fully discredit the professional work the team has conducted.

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Nevertheless, as time progressed, new tests were conducted, providing new evidence and deepening the controversy related to the site. In 2004, for example, researcher Sam Van Landingham conducted extensive bio-stratigraphic analysis, confirming that the strata that bore the discovered tools was some 250,000 years old. He re-confirmed these finds once again in 2006. He states in his papers that the samples can be dated to the so-called  Sangamonian stage  (from 80,000 to 220,000 years before present) due to the presence of several diatom species only appearing in that age. More findings appeared in 2008, when paleomagnetic testing was conducted on the volcanic ash layers from the site, dating them to roughly 780,000 years before present.

Hueyatlaco remains a true scientific anomaly. It is not at all impossible that early man could have crossed over to the Americas much, much earlier than is currently believed. In fact, there already is the conundrum of the  Solutrean theory , which tells us that the  Clovis people , the proposed ancestors of the Native Americans, were  not the first inhabitants of the Americas. Besides these, there are numerous pieces of evidence across the continent that tell us that it is nigh time that we reconsider the history of human habitation in the Americas.

Top image: The results discovered at Hueyatlaco remain controversial even today. Source:  Kovalenko I  / Adobe Stock

By Aleksa Vučković

References

Meltzer, D. 2009.  First Peoples in a New World: Colonizing Ice Age America . University of California Press.

Steen-McIntyre, V. and Fryxell, R. and Malde, H. 1981.  Geologic Evidence for Age of Deposits at Hueyatlaco Archaeological Site . U.S. Geological Survey.

Various, 2016. “Early–Mid Pleistocene environments in the Valsequillo Basin, Central Mexico: a reassessment” in  Journal of Quaternary Science .

Zillmer, H. 2010.  The Human History Mistake: The Neanderthals and Other Inventions of the Evolution and Earth Sciences . Trafford Publishing.