Nature paper suggests humans inhabited North America 130,000 years ago

April 27, 2017 • 5:43 pm

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.

26 thoughts on “Nature paper suggests humans inhabited North America 130,000 years ago

  1. As I pondered in the earlier thread…even if the stones were used as tools to break the bones, how confident should we be that humans were the ones wielding the stones as tools?

    Not only are humans far from the only tool-using animals on the planet, but I’m sure almost everybody reading these words has personally observed modern elephants, close relatives of the mastodons in question, manipulate comparable objects with their trunks. Finding much more sophisticated examples of elephantine tool use is not at all difficult — and that’s just limiting ourselves to the same species as is the subject of the “crime,” so to speak.

    Is there anything about the stones that demonstrates human-level craftsmanship rather than simple opportunistic use?



    1. (And I’ll again note that these tools are more primitive than ones dating back half a million years. How plausible is it that a select small group of humans would have the wherewithal to make a once-in-an-hundred-thousand-year voyage but would be suck with half-a-megayear-outdated technology? — b&)

      1. I don’t think the evidence for humans this early in North America is very convincing, but I will alert you to modern, and frequent examples of tool use in science.

        In a lab, we are surrounded by extraordinary technology, but anyone who has built several experiments from scratch will attest that improvisation is a necessary part of how experiments are built. Often very low ranking technologies / tools are used to when either time or money or space or not sufficient.

        It is more likely humans to find a 1960’s Thunderbird in an abandoned parking lot than a brand new Tesla.

    2. The ‘knapped’ tools are very crude. Given the kinds of humans around at the time, there should be hand axes or something similar.
      The idea that other mastadons may have altered the bones is interesting. Elephants handle elephant bones, and I can see how that would make the markings on the bones.

      1. Hand axes are quite uncommon and even absent in sites from Asia associated with H. erectus or other hominins. This may be due to a lack of suitable raw material and other have proposed that bamboo was an abundant and superior material for tools. But, bamboo tools wold not preserve in the archaeological record. But I do agree that this site should have some clearly recognizable stone tools if it really is evidence of hominin activity.

  2. I haven’t read up on this but how can they rule out that the mastodon skeleton wasn’t hacked on by humans 100k years after it died?

  3. From an articule in BuzzFeed News by Dan Vergano, which Michael Shermer tweeted:

    “The extraordinary claim, made about a prehistoric bone bed under what is now a highway outside modern-day San Diego, would set back the age of the first human ancestors in the Americas by more than 100,000 years.
    But a slew of independent fossil experts contacted by BuzzFeed News think the report, published on Wednesday in the journal Nature, is crazy.
    “I have read that paper and I was astonished by it,” archaeologist Donald Grayson of the University of Washington told BuzzFeed News. “I was astonished not because it is so good, but because it is so bad.”
    The far more likely explanation, according to Grayson and other skeptics, is that the bones were crushed not by ancient humans, but by bulldozers carving a new highway in the 1990s.”

  4. Why is it so hard to imagine hominids getting here in principle that long ago? NA doesn’t seem the hardest place to get to. Also, SA workers have a long tradition of postulating older than Clovis dates (not even considering Monte Verde). Why should this be so surprising? A hangover from the Clovis Cops?

    1. What’s surprising is not that they got to Southern California 130,000 years ago, but that having done so, they left no further trace of themselves for the 100,000 years.

  5. Not impossible, but before taking serious such an extraordinary claim there should be much much more evidence.

    In the past there has been created a lot of science fiction on wrong evidence.

    But still interesting.

  6. It is a datum to remember for sure. But I read the BBC article where they found archaeologists – who has not seen the evidence I think, but can comment in general terms – that it would be difficult to exclude natural stone impacts of some kind. The paper apparently argues against that on grounds of a low-energy deposition regime, but again that must be hard to totally exclude.

    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.

    It could also be population bottleneck effects. At least one of the latest papers on the Neanderthal alleles – which reference I have to dig up – cannot exclude the introgression of such basically drift alleles (from small population sizes) into a larger and increasing population as the cause of their rarity as opposed to breeding barriers as such. On such a background I could expect indigenous Americans to have more of such alleles.

  7. I read a lot of papers on human origins in archaeological journals in 1989-90 and noticed a very clear tendency for authors to go way beyond the strength of the evidence in their claims about what was shown by the site they had just excavated.

    This looks very reminiscent of those papers.

    Here is a theory, which is mine:

    “In many ways the problem is that what are in reality tentative hypotheses are being presented almost as facts.”

    Journal of Archaeological Science, 1993

  8. Without shaped stone tools I also am dubious. As I understand, it is very hard to distinguish between the oldest shaped unshaped tools – handy sized rocks in other words – & ordinary rocks that are left by natural processes. Indeed, who has not picked up a stone & smashed it – often it looks little different from a stone that has not been picked up & smashed by a human.

  9. What is the possibility that a small band of early migrants crossed over into NA and then just died off or simply melted into the landscape? How many people would it take to maintain a small breeding group…perhaps a couple of hundred? What are the chances that we’d find multiple sources of evidence of so small a group?

  10. If those bones show signs of breakage soon after death, why is there a complete lack of evidence showing any cutting and scraping to remove the meat from the bone? This does not appear to add up in any sensible manner.

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