Megafaunal Extinctions

Friday, January 4th, 2013

When competent human hunters encountered naive fauna, the biggest animals,  things like mammoths and toxodons and diprotodons, all went extinct — which leads Gregory Cochran to make some larger points:

It is not hard to see why this occurred. Large animals are more worth hunting than rabbits, and easier to catch, while having a far lower reproductive rate. Moreover, humans are not naturally narrow specialists on any one species, so are not limited by the abundance of that species in the way that the lynx population depends on the hare population. Being omnivores, they could manage even when the megafauna as a whole were becoming rare.

There were subtle factors at work as well: the first human colonists in a new land probably didn’t develop ethnic/language splits for some time, which meant that the no-mans-land zones between tribes that can act as natural game preserves didn’t exist in that crucial early period. Such game preserves might have allowed the megafauna to evolve better defenses against humans – but they never got the chance.

It happened in the Americas, in Australia, in New Zealand, in Madagascar, and in sundry islands. There is no reason to think that climate had much to do with it, except in the sense that climatic change may sometimes have helped open up a path to those virgin lands in which the hand of man had never set foot, via melting glaciers or low sea level.

I don’t know the numbers, but certainly a large fraction of archeologists and paleontologists, perhaps a majority, don’t believe that human hunters were responsible, or believe that hunting was only one of several factors. Donald Grayson and David Meltzer, for example. Why do they think this? In part I think it is an aversion to simple explanations, a reversal of Ockham’s razor, which is common in these fields. Of course then I have to explain why they would do such a silly thing, and I can’t. Probably some with these opinions are specialists in a particular geographic area, and do not appreciate the power of looking at multiple extinction events: it’s pretty hard to argue that the climate just happened to change whenever people showed when it happens five or six times.

It might be that belief in specialization is even more of a problem than specialization itself. Lots of time you have to gather insights and information from several fields to make progress on a puzzle. It seems to me that many researchers aren’t willing to learn much outside their field, even when it’s the only route to the answer. But then, maybe they can’t. I remember an anthropologist who could believe in humans rapidly filling up New Zealand, which is about the size of Colorado, but just couldn’t see how they could have managed to fill up a whole continent in a couple of thousand years. Evidently she didn’t understand geometric growth. She is not alone.

Should you ever be desperate and in need of game, Jehu adds, take a copy of the hunting regulations for your state:

Look up all the hunting methods and tactics that are banned. Those are the ones that your lower-tech ancestors would have used. They’re banned precisely because of their effectiveness and efficiency.

Dave Chamberlin continues in that vein:

Fish are damned tasty and also damned stupid; they have never learned that swimming up to a bright light during night time frequently gets them caught on the end of a spear. Fisherman are pissed off that American Indians are still allowed to go fishing this way because it is so easy and so effective.

Sharpening a stick with a knife (or a piece of flint if you want to be historically accurate) it is really easy to incomplete a cut that leaves a perfect barb near the point that would keep a fish from sliding off the spear.

Fire made food far more digestable, but it also kept us warm, protected us at night, and made fish so easy to catch it’s now considered cheating. No wonder Homo erectus spread out far beyond Africa.

Leave a Reply