Our species evolved in Africa but as you may have noticed, we didn't stay there. Over the past 100,000 years, we've been expanding around the globe. One of the last stops on this grand voyage was America. The first Americans arrived via Beringia, around 15,000 years ago. Or did they?
Early in 2017, archaeologists found a 130,000-year-old site in California. Which is a fair bit older than the first Americans should be (130,000 being a larger number than 15,000). Obviously, this threatened to shake things up; making international news in the process.
A few months passed and the dust has settled. Other scientists have had time to pour over these findings. Their conclusions? The first Americans probably didn't arrive so long ago. The evidence is ambiguous and the ancient date might be as reliable as we thought.
The Cerutti Mastodon
The discovery that's causing all this fuss is a 50 square metre area near State Route 54 in San Diego. This nondescript spot was having a new sound barrier installed, but as excavation commenced, supervising archaeologists spotted something in the ground. This led to the discovery of more than 300 mastodon bone fragments, along with a handful of bits of rock, earning the locale the name "Cerutti Mastadon Site". Or the less memorable, SDNHM locality 3767.
Crucially, the bones look like they've been hit with something, and the rocks appear to have been used to hit something. This is classic evidence of hominin activity as we're the only group that butchers meat with tools. Th/U dating of the Mastodon fragments revealed them to be 130,000 years old. Which, like I said earlier, is kind of a big deal for a site in California.
The archaeologists found no other evidence of human activity at the site. In fact, no other equally ancient activity has been found in America since. As such, all the evidence for early first Americans rests on these bones and rocks. So to confirm they were right, the discoverers smashed other bones with other rocks to see what the damage would look like. They found key similarities between their experiments and these ancient rocks.
Crucially, a powerful blow broke these large, thick bones. This is more force than any contemporary carnivore could produce. Trampling couldn't do it either, given many of these fragments are fragile ribs that wouldn't survive the process. The results seem solid. Humans were doing something in California more than 100,000 years earlier than they should have been.
Challenging ancient first Americans
So, all of this evidence looks fairly solid. How can people doubt it? Well, the critiques break down into three main areas. How sure can we be people did the damage? How sure can we be of the dates? And where's the context?
Criticism of the dating comes with any new discovery, particularly when it's controversial. However, I don't think this critique has much merit. Several bones were dated with different techniques. Although most approaches failed (as the bones were too old) this thoroughness suggests the results are valid. However, the other two points have a bit more merit.
For instance, how can we be sure that humans really caused this damage? Sure, they did a bunch of experiments showing that humans could cause this damage. However, none of these tests featured natural rocks for comparison. They didn't use a naturally damaged rock "placebo" as a control. As such, we can't rule out many alternatives. Plus, we have to remember that natural forces aren't the only ones at work in this case. They found these fossils and bones at a construction site after all.
Connected to this is the fact that the tools don't really follow the pattern expected of human activity at this period. Whilst early hominins did use these basic hammers and anvils, that was closer to 3 million years ago. By 130,000 years ago people were using shaped stone tools. Although they may have supplemented these with simple, expedient objects, carefully designed tools were the bulk of their toolkit. Yet they didn't find a single one at the site. Only the basic hammerstones.
The biggest flaw
This lack of archaeological context is, I think, the real reason for skepticism here. By 130,000 years ago hominins had a complex culture, including early signs of art. In Africa, they've left behind literally trillions of stone artefacts.
Yet despite all of this complex culture, the only trace these first Americans left were a handful of hammers in a Californian ditch. No other bones or tools anywhere else in the continent. They left no genetic traces in subsequent populations. No cool paintings in any of the caves.
And it's not like people haven't been looking for this. There are more than 10,000 archaeologists working in America and the idea of ancient Americans has been investigated since the 60s. Surely we would have found something else.
After all, that's the way it works with actual archaeological discoveries. In 2005 a similar situation played itself out. Bones with hominin-like damage was found in Gona, Ethiopia. This suggested Australopithecus did use stone tools. Around a decade later Australopithecine stone tools were actually found, confirming this theory. For context, scientists found the Cerutti site even earlier, in 1993. Yet there's been no such follow-up.
So after more than 20 years of failure to find another case of these first Americans, I think we can finally move on.
References
Braje, T.J., Dillehay, T.D., Erlandson, J.M., Fitzpatrick, S.M., Grayson, D.K., Holliday, V.T., Kelly, R.L., Klein, R.G., Meltzer, D.J. and Rick, T.C., 2017. Were Hominins in California∼ 130,000 Years Ago?. PaleoAmerica, 3(3), pp.200-202.
Haynes, G., 2017. The Cerutti Mastodon. PaleoAmerica, 3(3), pp.196-199.
Holen, S.R., Deméré, T.A., Fisher, D.C., Fullagar, R., Paces, J.B., Jefferson, G.T., Beeton, J.M., Cerutti, R.A., Rountrey, A.N., Vescera, L. and Holen, K.A., 2017. A 130,000-year-old archaeological site in southern California, USA. Nature, 544(7651), pp.479-483.
