One of the longest standing debates in modern archaeology deals with the mystery of human arrival in the Americas. Such mysterious human migrations were once thought to have conclusively rested on the premise that early human hunter gatherers crossed the Bering Land Bridge en route from Siberia, entering the North American continent and dispersing outward from there. However, the possibility that multiple entry points might have occurred, via ancient seafarers who sailed all along the Western coastlines, cannot be ruled out. The same must be said of those more controversial theories involving ancient sailors from Europe—possibly members of the Solutrean culture—making their way across the Atlantic and entering from the northeast.
In likelihood, there were many cultures and people who entered North America in the ancient past, arriving from a much wider variety of locations than once thought. What brought them to the Americas may remain somewhat mysterious, although it seems evident that the ancient quest for sustenance pushed them onward, and the discovery of lands rich with vegetation and, of course, megafauna kept them there. However, one of the greatest and most perplexing questions about their arrival that remains has to do with who the first arrivals were, and more specifically, when did they arrive?
The presence of archaeological sites associated with the Clovis culture, as well as a growing number of sites that present evidence of even earlier habitation, have continued to push back the timeline on early human arrival in the Americas. Among the best evidence for such discoveries have been bifacial stone tools (that is, projectile points or stone knives worked on both faces of the blade) discovered throughout North and South America, often found alongside or in situ with extinct animal remains; the earliest, and still among the most famous of these had been discoveries of megafaunal butchering sites at Folsom, New Mexico, and later discoveries at nearby Clovis, which established the thusly-named Folsom and Clovis cultures in the early part of the last century.
However, evidence of earlier lithic types also turn up in the mix from time to time. In 1967, a most unusual artifact turned up at a Mexican archaeological site at Tlapacoya, just south of Mexico City. The stone blade, made of obsidian, was radiocarbon dated to around 21,000 BCE, and helped establish the existence of a Mesoamerican pre-bifacial-point horizon in the region, further suggesting much earlier occupations in the region than once thought.
Tlapacoya was not the only location in the region that presented unusual ancient discoveries. Near Puebla, in what is called the Valsequillo region of Mexio, excavations similarly turned up unifacially worked stone tools that dated back to at least 21,800 years BCE.
The Valsequillo region, despite its confirmed antiquity, has remained somewhat controversial in archaeological circles. 21,800 years BCE is not an inconceivable time period for early human habitation, nor is it by any means the earliest suggested time of human settlement in the Americas. Recent controversial discoveries at the Cerutti Mastodon Site in Southern California were the latest to argue a much earlier human presence in North America, going as far back as 130,000 years. Understandably, most in the archaeological community simply cannot accept this, and the veracity of the alleged evidence of human butchering found at the site remains in dispute.
However, decades before the recent discoveries in California, a more obscure Mexican site at Valsequillo managed to arouse similar controversy for boasting an even greater potential antiquity for humans in the region… perhaps going back more than 100,000 years earlier than that which has been claimed for the Cerutti site.
The Hueyatlaco archeological site, also found in the Valsequillo Basin near Puebla, Mexico, achieved notoriety following excavations which began there in the 1962, carried out by Cynthia Irwin-Williams, who was co-discoverer of the site with Juan Armenia Camacho. The excavations, carried out in association with the U.S. Geological Survey, recovered a number of stone tools, some of which were discovered in situ alongside animal remains. Virginia Steen-McIntyre, a graduate student at the time, joined the excavation team during continuing excavations in 1966, following a request of Harold E. Malde, the on-site geologist; Steen-McIntyre would later become known for being associated with the site.
Among the most controversial of the ancient tools recovered from Hueyatlaco were those discovered in situ with the pelvis bone of a camel. Radiocarbon dating and geochronological analysis of the site, carried out during the 1960s excavations, led the archaeologists there to a startling determination: that Hueyatlaco, the scientists believed, dated as far back as 250,000 years before the present (specifically, the stratum where artifacts were recovered, according to radiocarbon dating, were found to be more than 35,000 years old; uranium dating of the same regions found dates believed to be around 260,000 YBP).
Shortly after publication of these findings, archaeologists in the region attempted to dispute the finds, suggesting that artifacts might have been planted at the location by local farmers (an assertion for which there appeared to be little corroborating evidence). A less conspiratorial suggestion from the greater archaeological community held that with the prevalence of fluvial deposits and flooding at the site, contamination of the stratum used for testing seemed more likely; this position is maintained by the majority of archaeologists today.
According to a later study that was published in 1981 by Virginia Steen-McIntyre, Roald Fryxell, and Harold E. Malde, examination through tracing of the stream beds at the site (performed during excavations carried out in May of 1973) showed they were present beneath 10 meters of water-laid deposits. Bifacial tools were discovered in the oldest of four units at the site, located within a channel covered with stream deposits.
Based on this information, the study’s authors concluded the following:
Fission-track ages on zircon phenocrysts from two of the younger tephra layers (370,000 ± 200,000 and 600,000 ± 340,000 yr) agree with concordant uranium-series dates for a camel pelvis that was found associated with bifacial tools at Hueyatlaco… These dates are compatible with the depth of burial and subsequent dissection of the Hueyatlaco deposits, as well as with the degree of hydration of volcanic glass shards and with the extent of etching of heavy-mined mineral phenpcrysts from within the tephra layers.
These findings suggest to us that further search for archaeological remains in deposits as old as those at Hueyatlaco would be warranted.
Of course, Hueyatlaco remains an item of heavy dispute within the archaeological community, since dates as early as those suggested at the site push back the timeline of human presence in the Americas by not just thousands, but potentially hundreds of thousands of years. Even with the level of academic rigor that has been applied at the site since the 1960s, conventional attitudes among archaeologists are far from near being able to accept such claims, particularly in the absence of other locations that would offer convincing evidence of similar antiquity.
Which, it is worth noting, brings us back to locales like the Cerutti Mastodon site in Southern California, a location believed by its excavators to represent far more recent early human presence, though one that still falls far from hitting the mark of credibility with most academicians. Perhaps with time, at least some of these early, anomalous archaeological sites will be revisited, and eventually confirmed as having shown evidence for much earlier arrivals and settlement in the West than most would ever have expected.
Until that time, Hueyatlaco will remain an anomaly, and one of several footnotes in the contentious ongoing debate about the earliest human arrivals in the New World.