Monday, October 24, 2011

We had a bone to pick

Here's the BBC report of a story relatively out of our realm of expertise (that is, we're totally ignorant in this area).  An archeological find that was discovered 30 years ago, and just reported in Science, has been dated, and casts some doubt on a struggling theory of the age of human habitation of the Americas, and the apparent subsequent disappearance of many mammals, like mastodons.
Recent studies have strengthened the case that the makers of Clovis projectile points were not the first people to occupy the Americas. If hunting by humans was responsible for the megafauna extinction at the end of the Pleistocene, hunting pressures must have begun millennia before Clovis.
Mastodon rib with the embedded bone projectile point. (A) Closeup view. (B) Reconstruction showing the bone point with the broken tip. The thin layer represents the exterior of the rib. (C) CT x-ray showing the long shaft of the point from the exterior to the interior of the rib. (D) The entire rib fragment with the embedded bone projectile point. (From Science, subscription required.)

It was once thought that 'we' (that is, Native Americans) got here around 12,000 years go.  Shortly thereafter, many large animal species disappeared.  People using a particular projectile style called Clovis points were argued by some to have hunted mastodons and other large species to extinction.  Others argued that we couldn't have driven such species to extinction, and it must have been some other kind of ecological changes that were responsible.

Accumulating evidence is that humans got here somewhat earlier than had been thought, but it was still questionable what happened to the Big Game species.  The latest evidence dates a mastodon killed (or at least wounded) by a human-made projectile to an early time and suggests that humans did, at least quickly learn to hunt these beasts, before the appearance of Clovis-style tools.

So, we arrived and bye-bye mastodons!  Now, humans had been in the Old World for millennia upon millennia, and it's no surprise that those who could manage in the arctic climate, work their way across the Bering land bridge (presumably in part by hunting migrating game) knew how to hunt the ground-dwelling species they found here.  They had to have eaten something, after all, even in the winter!

The interesting thing to us, who are not archeologists and haven't been involved in debates about timing, Clovis, and so on, is whether this find just shows that we hunted big things like mastodons, or whether we were responsible for their total demise.  Or whether climate or other changes (related to those that produced the Bering land bridge?) were in the main responsible.

Let's assume humans are guilty.  How can this be?  How can the relatively sparsely distributed hunting bands at that time (and there's no evidence for anything more dense and sophisticated than such groups) have tracked down and killed off all of several species?  After all, the ancestors and contemporaries of the New World settlers didn't exterminate all large land mammals in the Old World.  And many species in the New World (bison, deer, and others) were doing very well for long time after our first appearance.  Bison disappeared, current wisdom has it, only when the Indians gained horses from atop which to slaughter on a large scale.

Could this be the phenomenon of new immigrants doing in species that had not adapted to them as predators? If so, what was different about that, since clearly there were also predators in the New World, so it wasn't Shangri La for mastodons.  Or were mastodons too, well, mammoth for sabre tooth tigers to mess with?  This new find shows earlier evidence of human predation but does it change these questions themselves?   Presumably the professionals (not us) will have things to say about this.


n8craig said...

I have a couple of reactions to this post. 1) Monte Verde is a widely accepted pre-Clovis site in Chile. Residents at Monte Verde, a very well preserved site, did not seem to be pursuing pleistocene megafauna. Instead, there are a surprising number of plant and small animal remains. 2) I think it was likely US citizens engaging in mass buffalo slaughter that produced the drastic decline in buffalo population. There are some enormous indigenous pre-equestrian, in fact paleoindian, bison kill sites. Olsen-Chubbuck is one example. Despite these massive kill sites, there were substantial buffalo populations into the historic period. The equestrian plains adaptation may have contributed some to dwindling bison populations. However, from my reading of history it was largely "whites" who are responsible for decimating plains bison populations. This was through a combination of market hunters and wholesale slaughter of herds that were sanctioned and endorsed by the US Army. Part of the strategy was to weaken the economic base of plains people--to make it easier to conquer and dominate them. A severe draught that lasted from 1845-1860 probably also played a role in decimation of plains bison herds.

The blog comments don't seem to permit me to hyperlink text. Here is some easily accessed reading from the internet. References supplied provide more information those who are interested.

See the linked photo.

Ken Weiss said...

There's some confusion here. We were discussing the extinction of things like sabre-tooths and mammoths, not bison. There it is clear that while the Indians, esp. Comanchee after the horse was brought in by the Spanish, started the decimation, and the railroaders all but finished them off.

n8craig said...

I was responding to this specific quote, "Bison disappeared, current wisdom has it, only when the Indians gained horses from atop which to slaughter on a large scale." With all due respect, this is not my understanding of current wisdom or a reflection of the historic record. I'll admit that my knowledge of the subject is limited. However, I understand that the US government had a large and very active role to play in killing off bison. There was a specific program that sought to weaken the economy of plains people. There is strong archaeological evidence of economic intensification (and increasing gender disparity) with the adoption of horses. But the systematic killing of bison as a political and military tactic is, in my humble opinion, significant. Especially in the context of the aforementioned quote. Just my two bits...

Ken Weiss said...

Yes, that was a wording mistake on our part. I had just finished reading Empire of the Summer Moon, about the Comanchees. That recounted the story of the bison. It correctly identified the US gov't and railroads, as you say. Our point in the blog post was that even that kind of dramatic, modern technology nearly, but not even completely, finished off a flourishing species.

So we were wondering how pre-industrial, pre-horse Native Americans could have been responsible, even if they did in fact hunt the mammoths. One could cite Africa and Eurasian generally in that human predation has been there a long time but without causing mass extinctions. So how did the Native Americans manage it, if they were responsible.

Again, however, thanks for spotting the error on our parts.

hollis said...

I've always wondered if humans coming to North America brought new diseases with them -- to which those large mammals had little or no resistance. It certainly happened later, when Europeans reached the New World bringing disease that decimated local populations.

Ken Weiss said...

Probably not. They had to pass through a long, many generations wide, 'arctic corridor' (I forget the term) that prevented that type of pathogen to survive the trek--no intermediate host in pre-agricultural populations, etc. Populations were too small and sparse for contagion to work.

The Native Americans when seen by the first whites did not have the kind of contagious diseases we did. We know ours devastated them because they weren't previously exposed, but not the other way round (except, perhaps, for syphillis, and I think that's somewhat debated). This, more or less, is the standard story, I believe.

Whether accompanying dogs or something may have carried disease, that would have affected other mammals here, I know not.

In any case, if such a thing happened, I have not heard any credible scenario to that effect. The extinction times were also (as my imperfect understanding has it) too slow relative to that and too closely tied to Clovis culture, to harken back to something brought in 20,000 years ago.

Maybe some other MT reader would know....