On any given day I spend, oh, roughly zero percent of my time thinking about evolutionary psychology. Not because it's not fun: it is, but it just seems like you can make up anything at all to "justify" the mental trait you're trying to explain. (My innate inability to stay focused on whatever task I'm supposed to be doing, for example, proved crucial back in the Plumer family's savannah days, when the hunting party next door would be too fixated on the mastodon in front of them whereas only we would notice the lions who attacked from the sides.) Maybe that's not what real researchers do, but it sure seems so. Jerry Fodor's essay in the Times Literary Supplement, meanwhile, fires off a few more serious criticisms.

That said, it's hard to deny that human behavior probably did result in part from years and years of evolutionary pressure and oft-unfortunate encounters with various mastodon-like beasts. One of the places that understanding this might actually come in handy, perhaps, is in thinking about "irrational" economic behavior. Much of human behavior, after all—at least the bits that reduce down to biology—evolved long before we ever even had things like property rights and currency and whatnot. It's possible that this mismatch could explain quite a bit. For instance, studies show that people tend to prefer, say, $20 today to $40 a month from now. Seems sort of dumb. But of course, back on the savannah, there were no such thing as promises or futures contracts. "$40 a week from now" just didn't exist! By then, your lender would be eaten by the lion.

Meanwhile, prospect theory tells us that people hate a loss more than they enjoy a gain of equal value; or, alternatively, that people value something more once they own it than they do when trying to acquire it. Wacky humans! But naturally, back in our spear-throwing days, property rights didn't exist, and things weren't really tradable. No, you simply had your nasty, brutish, and short battles for territory. And territory you own is more valuable than territory you're trying to acquire—because, for instance, you spent so much time pissing on all the trees to mark it, or simply because it's easier to defend. As it turns out, an anonymous source familiar with ongoing biological discussions recently told me that this really does happen among birds: they'll fight harder to defend territory than they will to acquire it. So there. Okay, I'm mostly joking about all of this, but I don't see why it's so surprising that a species that evolved over millions of years to behave "rationally" in a world without land deeds and money shouldn't do some distinctly irrational things now.