People v. Megafauna (Book Review)

One of the more interesting intersections in earth science is at the end of the Pleistocene some 10,000 years ago in North America.  Trying to untangle the climate and human changes at this time is challenging in no small part because you are dealing with experts in archeology, paleontology, and paleoclimate (there is even a small role for solid earth geophysics if you look carefully) as well as cultural clashes over ethnic heritage and, occasionally, legal battles.  It is where GG’s Historical Geology class really starts, so a book really digging in to this material is always welcome.

David Meltzer’s First Peoples in a New World: Colonizing Ice Age Americais a rarity as the author is a working archeologist and the text doesn’t try to gloss over disagreements but instead fleshes out arguments too often presented as disagreements between personalities. Although the book is now five years old and so missing some recent discoveries, by and large this covers the big issues in the original peopling of North America as they still stand today.

The book examines the first evidence for humans in the Americas, compares means of identifying (or misidentifying) the timing and constitution of the wave or waves of immigrants to North America from Asia, continues to consider the implications of the widespread Clovis point, and explores the early differentiation of cultures near the dawn of the Holocene. Linguistic, archeological, ethnological, physiological, climatological, microbiological, geochronological and geologic evidence are all brought before the reader at a reasonably nuanced level. The author walks a tightrope between being too personally present in the story and being too distant, between advocating his point of view and presenting conflicting views; for the most part this is successful even when your point of view might not mirror the author’s. Since he is a player in this saga, his appearances in the text are not as gratuitous as when an outside science writer employs National Geographic style “I am here” moments.

Consider, for instance, the question of what the earliest evidence for human occupation in the Americas is. Rather than diving in to modern arguments over specific sites or outright dismissal of some as not worth discussion, Meltzer reviews the early hunt for human occupation of Ice Age America.  This quickly hones in on the Folsom site in New Mexico where the first evidence of human coexistence with extinct fauna was found. The dispute over that site and what finally made it convincing enough to win over skeptics sets the stage nicely for discussion of the more recent claims of more ancient evidence of humans.  Where media reports of such finds often are limited to a claim, a mention of an interpreted artifact, and a counterclaim (often without context), here we see the breadth of issues that can cloud a claim, which makes far clearer why many such claims end up failing to achieve general acceptance. And, in the end, why Meltzer (at least) was convinced by the pre-Clovis Monte Verde site in South America, a site which plays a prominent role in the discussion.

Of course, being the product of a working scientist, Meltzer’s biases do intrude somewhat.  Perhaps the most glaring case is his dismissal of humans as the cause of the extinction of the megafauna.  From a geologic perspective, this seems by far the most parsimonious explanation: we have many previous deglaciations without major extinctions, but only the last one (the one with people) produces a major American extinction event (but at most a minor European one and no African or Australian one), and an odd one at that (the rate of extinction of smaller mammals remained at essentially the same level as through the rest of the Pleistocene). Could it really be that different than the others? Meltzer boils this down to a single hypothesis for human-caused extinction: Paul Martin’s blitzkrieg or overkill hypothesis.  He writes “None of the factors that make island life vulnerable to extinction apply to North America….If humans drove North American animals to extinction, it had to have been by their spears, as Martin said” (p. 259). The remainder of the considerable discussion is about the relative dearth of slain animals in the archeological record: in essence, Meltzer has replaced the question of whether humans caused the extinction with how humans might have triggered extinctions, answering (without any real evidence) that it must have been by hunting, and then, having chosen a preferred straw man, he hacks at that target, assuming that this must answer the question of whether humans killed off these fauna. This is understandable in view of Martin’s prominence and strong adherence to his overkill hypothesis, but it does a disservice to the reader and the rest of the community. This feels like the comfort of fighting the battle you know well and ignoring the war elsewhere; for instance, there is (and was when the book was written) a decent argument to be made in Australia that extinction there was largely by the introduction of fire.  As for “there is absolutely no evidence Clovis people caused massive (or even minimal) environmental destruction,” are you sure you know what you are looking for? During a time of unquestioned climatic turnover and armed with much less information about what the previous interglacial looked like, are you sure you aren’t conflating climate and human actions? It seems plausible that many of the changes in biota have been interpreted as due to climate simply because nobody ever proposed the change as being from human activity (see the post on the sequoias).

And, of course, science marches on; one objection of Meltzer, that there is no evidence of camel or horse kills (p. 260), would seem to be refuted by camel and horse DNA on Clovis tools found in Boulder; it would quite the coincidence to find the one set of tools that was used in slaughtering a horse and camel if this was a completely rare event. A 2012 review of the question of the relative role of climate and human activity indicted both as being significant players; similarly, a 2009 study showed that the 35 extinctions could all be simultaneous.  Instead of the overkill hypothesis being dead and buried (as, it would seem, the archeological community viewed it), some broader version of this looks like a very robust hypothesis.

Anyways, while that one point clearly grated, the book is one of the most readable you will ever find dealing with this material at this high a level.

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