I wish there was convincing evidence of human occupation of North America 130 000 years ago in the recent Nature paper on the Cerutti Mastodon find (Holen et al 2017). The bottom line is that there isn’t. The dating of the Mastodon itself is uncontroversial because it is plausible, although it is somewhat less than completely secure (Yong 2017, Archaeometer). The real debate is about the claimed evidence of human activity at the site. This falls into two classes: 1) Evidence of human processing of the mastodon bones and 2) stone tools recovered at the site.

The bones

The claim that the bones are processed is supported through experimental archaeology. The authors claim that they can demonstrate the presence of humans because their experimentally broken bones fit the excavation data both in fracture pattern and in spatial distribution. Here the authors make a simple but fundamental error. Experimental archaeology results can be used to rule out possibilities but not to confirm them. When Barnes (1939) demonstrated through experiment that Pliocene flints interpreted as human-produced tools could in fact be replicated by natural processes, he was not confirming that they were not tools; he was simply failing to reject the hypothesis that they were naturally produced. This firmly established that natural production remained available as an explanation for the presence of eoliths, or tool-like objects in Pliocene contexts. Human intervention was not necessary. It didn’t mean that Pliocene humans had not existed, but in the absence of any other evidence such as fossil remains, it established that they were unnecessary. Holen et al (2017) show that the Cerutti Mastodon bones could have been fractured by stone tools. They don’t show that they were.

The tools

Speaking of eoliths, the stone tools claimed by Holen et al (2017) are unfortunately much less than convincing, at least in the images available with the article. We’re admittedly quite far from any sort of Mousterian complex, for example. Just as in the case of the bones, none of the modifications shown strictly require human activity.

Some of them could certainly be the result of tool making and tool using by people. But they need not be. And that is just not enough for claiming an archaeological site in North America 130 000 years ago. Not only is that very nearly an order of magnitude older than any other solid find, it requires that we find an entirely new explanation for how humans got to the Americas, for how they remained largely archaeologically invisible for at least the next 110 000 years, and for why we find no genetic evidence of those early arrivals. That’s a lot of explaining to do on the basis of very equivocal evidence.

The bottom line

I have no problem with the idea that there might have been human ancestors or cousins in the Americas in the Middle Paleolithic. However, the Cerutti Mastodon site is not a modern Folsom. I want to believe. But I just haven’t seen any evidence yet that makes it necessary.

In his Outline of the problem of man’s antiquity it North America, Howard (1936:395) tells us “…the old controversy goes on: did man come to America in comparatively recent times, or was he here before the last glacial period?”. He concludes his survey (Howard 1936:411) on the hopeful note “That he may have lived here earlier [than the last glaciation] cannot be denied, but the evidence is not yet ample enough to prove the case, so we rest it here”. And so do we.


Barnes AS 1939. The differences between natural and human flaking on prehistoric flint implements, American Antiquity 41:99-112.

Holen et al 2017. A 130,000-year-old archaeological site in southern California, USA, Nature 544:479-483.

Howard, EB 1936. An outline of the problem of man’s antiquity in north America, American Antiquity 38:394-413.

Yong E 2017. A new study says humans were in America 130,000 years ago, The Atlantic. https://www.theatlantic.com/science/archive/2017/04/new-study-puts-humans-in-america-100000-years-earlier-than-expected/524301/

18 thoughts on “The Cerutti Mastodon: Eolith redux

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