by Greg Mayer
As Jerry noted yesterday, in a new paper in Nature, Steven R. Holen and colleagues report finding the remains of a butchered 130,000 year old mastodon in San Diego. (If you haven’t already done so, do go take a look at Jerry’s post, which includes a video press release, and illustrations from the paper.)
The key words in the first sentence are ‘butchered’* and ‘San Diego’. The first word indicates that people had taken the bones of the 130,000 year old mastodon apart– which in itself would be a “neat, but what’s the fuss” result. It’s ‘San Diego’ that’s the cause of the fuss. The peopling of the Americas has been a contentious topic for some time, but virtually all the debate has concerned a relatively slim time interval– 12-30 kya (see here for a previous discussion at WEIT, and this news piece in Science about two recent papers with contrasting conclusions). The San Diego find is thus 100,000 + years earlier!
So what evidence do they have for this early arrival? First, they have the mastodon, whose bones were fractured in ways which they find inconsistent with damage by carnivores or the environment, but which appear consistent only with being struck with implements. They did a lot of breaking of elephant bones in order to try to simulate the damage to the mastodon, and concluded that tools alone could do the trick. The mastodon’s remains were radiometrically dated at 130.7 ± 9.4 kya. In addition to the mastodon, they also found stone tools, which they interpret as hammerstones and anvils.
These results would have many important implications for human evolutionary history; but first we must ask, are the results correct?
I must admit I’m dubious. The anvil and hammerstones are not the sorts of objects which are unquestionably manufactured– they are not like finely fluted spear points, whose human origin cannot be doubted. The breakage patterns in the bones do indicate that the breaks occurred perimortem, but I’m not sure the breaks could not be due to non-human causes. The dating is directly on the mastodon, which is good– they’ve not dated some possibly extraneous item which could have been redeposited from earlier strata. But, nonetheless, dating is subject to various artifacts.
As Carl Sagan used to say, “Extraordinary claims require extraordinary evidence.” What makes the current claim extraordinary is that there’s no other evidence of human presence in the Americas for ca. 100+ K years after this find. And it’s not like the late Quaternary of America is an unstudied or poorly known stretch of time! I don’t regard fracture patterns and crude tools to be sufficiently extraordinary evidence to overcome, in a single go, the weight of that 100,000 year absence. It is much more reasonable to think that the new data can be reconciled with all the past data in a way that does not require us to discount the past data. And, thinking, “they must have made a mistake somewhere with the new data”, is a perfectly plausible way of reconciling the two. This conservatism in the face of anomalies is a key part of the method of science– it properly proportions belief to the evidence.
On the other hand, the new data do not threaten to overturn any fundamental principles, merely a seemingly well-attested fact of evolutionary history, and such facts have been overturned before. So, we must ask, but what if they’re right?
The most interesting implication, to me, is that if there were people here 130 kya, they went completely extinct. It means that human habitation of an entire hemisphere is an iffy thing. The real first Americans got wiped out by something– disease, predators, climate, competitors, whatever. Who would these now extinct people have been? Well, if they got to America not too long before the radiometric date, they would probably be Neanderthaloid (by which I mean the varied archaic Eurasian subspecies of Homo sapiens with which anatomically modern humans interbred after their spread from Africa). If they came much earlier, they might have been Homo erectus (which would make Harry Turtledove’s A Different Flesh, in which the first European settlers of America encounter not Indians, but “sims“, prophetic!).
There would also be a possibility that these first Neanderthaloid Americans survived, and that the anatomically modern human colonizers of ca. 20 kya, interbred with them in the course of replacing them, just as their forebears did in Asia. However, because American Indians are not, as far as I know, enriched for Neanderthaloid alleles relative to other Eurasians (who are 1-4% Neanderthaloid; a bit higher in Melanesia), this seems unlikely. (There are claims out there that Indians are enriched for Neanderthaloid genes, but I don’t know how that got started; East Asians, from which, at least generally, American Indians descend, are Neanderthaloid enriched relative to Western Europeans, which seems to indicate more than one episode of interbreeding on the course of their migration from Africa.)
* I use “butchered” here in the sense of “processed for eating”, as the bones were presumed broken apart to get at the marrow. The paper uses “butcher” in the narrower sense of “cut with a knife or similar implement”. The paper does not say the mastodon was cut with a knife or other sharp tool.
Holen, S. R., T. A. Deméré, D. C. Fisher, R. Fullagar, J. B. Paces, G. T. Jefferson, J. M. Beeton, R. A. Cerutti, A. N. Rountrey, L. Vescera, and K. A. Holen. 2017. A 130,000-year-old archaeological site in southern California, USA. Nature 544:479-483.