Mammoth Discovery Would Double Timeline of Humans in North America

Hartley had been hiking a narrow game trail that followed the Rio Puerco, a small tributary to the famous Rio Chama, in northern New Mexico. The creek and game trail loosely bordered his neighbor’s property. Hiking with his eyes glued to the ground, he noticed white specks scattered across the red dirt, bone chips of unknown origin. Then, a glazed-black obsidian Clovis point.

Hartley realized he may have slipped off his own property, so he paid his neighbor a visit and filled him in on the discovery. As fate would have it, his neighbor, Dr. Timothy Rowe, is a vertebrate paleontologist in the Jackson School of Geosciences at the University of Texas in Austin.

The two of them went back to the Rio Puerco to poke around some more. They followed the bone flakes up a small wash and discovered mammoth tusks, molars, and ribs lying in concentrated assortments. In combination with the bone flakes and Clovis point, Dr. Rowe knew they had found something special.

Since its discovery, the Hartley Site has become the subject of numerous studies, which have examined everything from its geologic qualities to the source material used to craft the Clovis point. In July of 2022, Dr. Rowe and colleagues published their latest findings.

According to their research, published in the journal Frontiers of Evolution and Ecology, the Hartley Site contains unequivocal evidence that humans butchered those mammoth bones. The researchers even found bone implements handcrafted by humans and signatures of controlled fire. And that’s not all—the researchers claim that the site dates back 37,000 years, doubling the conventionally agreed-upon timeline for when people entered America.

The Debate

Since the publication of Dr. Rowe’s research, the Hartley Site has become the great spoon that stirs the peopling of the Americas debate, largely because it challenges the prevailing theory that humans arrived on the continent 16,000 years ago. It’s important to note that “prevailing” is a loose term here, because as the decades tick on, our understanding of human evolution evolves.

In fact, over the past several decades, the field has experienced a revolution fueled by technological advancements and climate change. Commonly held beliefs just a few years ago have become antiquated, and as technologies continue to advance, the turnover rate between old and new theories shortens.

At one point or another, nearly every anthropologist subscribed to the Clovis First theory. That theory states that people from the Clovis culture entered the Americas before all others. It’s substantiated by the arrival of intricate stone tools dating back 13,000 years. Around that time, Clovis people are said to have crossed the Bering Land Bridge from east Asia into modern-day Alaska. On virgin soil, the theory states, Clovis proliferated across the continent.

In 1977, Tom Dillehay excavated Monte Verde, a site on the southern end of Chile. He unearthed wooden architecture, stone tools, cooked plant remains, and even wads of masticated seaweed. Dillehay’s analyses dated the site to 14,500 years ago, predating the arrival of Clovis people by 1,500 years. The discovery shook the archaeological community at its foundation, and the Clovis First theory buckled, but Dillehay’s story wasn’t over. Nearly 40 years after its initial discovery, Monte Verde broke headlines yet again. Dillehay revisited the site and conducted updated research. His results, published in 2015, dated the site at 18,500 years old.

Between 2015 and 2019, researchers uncovered two more sites, one in South Carolina and one in Idaho. These sites became the oldest known to exist in North America, and scientists had dated both at roughly 16,000 years old. Then, in 2021, White Sands National Park challenged our understanding even further. Scientists conducted research on ancient footprints that followed the shores of an Ice Age lake. Those footprints, the researchers say, have been imprinted on the landscape for at least 21,000 years.

Now, we have the Hartley Site—a curious pile of mammoth rubble, peppered with peculiar bone flakes, in an unassuming corner of New Mexico that threatens to rewind the clock farther back than anyone ever thought.

The Evidence

Dr. Rowe and his team assert that the Hartley Site dates back somewhere between 36,250 and 38,900 years ago, as evidenced by the results of a carbon dating analysis performed on the collagen found in the mammoth bones. His team also examined microscopic features of the bones using high-resolution CT scans. They detected unmistakable signs of human butchering on a female mammoth and her calf, likely by use of stone and bone tools.

The bone scraps scattered around the site offered even more human evidence. As opposed to processes like natural weathering, the bone flakes seem to have resulted from boiling and crushing, a process used by ancient humans to extract marrow. Many of the bone flakes had sharp edges suitable for cutting and had been struck perpendicular to the grain, suggesting that they had been purposefully knapped off larger bone chunks. Some bore secondary scars, which result from refining crude tools. Others were wedge-shaped. Archaeologists call these butterfly fragments. Butterfly fragments result from blunt force impact to the bone. The force required to create a butterfly fragment rarely happens in nature, and almost always comes from a deliberate blow by humans. Researchers uncovered multiple butterfly fragments at the Hartley Site, some sourced from limb bones and others from the ribs.

Dr. Rowe and his team also examined the soil and found signatures of controlled fire. They uncovered bits of burnt wood, plant material, and bone. The sediment contained the charred remains of rodent incisors, fish scales, and fish teeth, despite the fact that the site overlooks the nearest river by over 200 feet. The presence of these remains, Dr. Rowe and his team suggest, supports the theory that humans created the fires, not natural processes.

You may wonder how that Clovis projectile point Gary Hartley found plays into all this—it only fuels the controversy. Since it bears characteristic features of most Clovis points, it likely dates back 12,000 to 13,000 years ago. Initially, its presence indicated that the Hartley Site may have been a Clovis site. In light of the carbon dating analysis, the researchers suggest that the soils at the Hartley Site mixed over time, landing the point coincidentally in the same wash as older human artifacts.

While Rowe’s research seems positioned to turn back the human migration clock, others aren’t so convinced. Allen Dart, Registered Professional Archeologist for the Old Pueblo Archeological Center in Tucson, Arizona, questions the validity of Dr. Rowe’s data and assumptions. In a Facebook post shared by the Illinois Association for Advancement of Archeology, Dart outlines his argument.

Dart points out that it’s unusual for a butchering site to have such a glaring lack of stone artifacts, especially given the site’s locale, which is situated in an area with high-quality stone tool material like Pedernal chert. Dart also highlights Dr. Rowes own clarification, found in the supplementary data PDF file adjoining his paper, that burrowing organisms could have brought deposits of stone flakes deeper into the soil, placing them serendipitously with the older mammoth bones. Dart believes that the paper presents an alarming lack of discrete evidence for human-induced fire. He interprets the collagen samples sent out for carbon-dating as having relatively low carbon content, meaning that the analysis could have been jeopardized, and he speculates that the site’s context, a result of numerous landslides, warrants further questioning and skepticism.

Lessons Learned

If the past few decades of anthropological discovery have taught us anything concrete, it’s that the Hartley Site serves as just the latest of what will be a long line of future discoveries that will continue to reshape our idea of the peopling of the Americas. With each discovery, our understanding broadens, more questions arise, and the complicated story of human migration unfolds. Anthropology is an imperfect field bent on continually revising old information, and the best we can do for now is keep up with the science and appreciate the imperfection of it all. Dr. Rowe emphasized this point in a recent press release.

“What we’ve got is amazing,” Dr. Rowe said, “It’s not a charismatic site with a beautiful skeleton laid out on its side. It’s all busted up. But that’s what the story is.”

Feature image via the University of New Mexico.