Extinction and taxes

There's not actually very much evolution in Robert Frank's The Darwin Economy. Frank takes a big idea from Darwin: the insight that success is relative, and so how much is enough depends on what everyone else is doing. But the deeper you go into the book, the less Darwin is mentioned. (Also, this something that economists must have already realized, because they've got a name for it: positional spending.) Essentially, it's a book about tax policy, and a very good one.

I've got a piece in Slate criticizing his biological examples (and spinning off from there). But I thought the writing about economics was excellent, partly because I'm not an economist and it was all clear to me. Not everything he advocates chimed with my prior prejudices — he argues (convincingly), for example, that goods should be allocated on willingness to pay, even though that might see them go to those we consider less deserving. But it's hard not to think that the world would be a better place if Frank were making tax policy.

Frank makes the point that an arms race and a tragedy of the commons are the same thing. Everyone is better off if everyone shows restraint, but any individual is better off if he or she alone cheats. So the rational thing to do is cheat, and everyone ends up worse off.

This is a connection that biologists have only just begun to make. In particular, Hanna Kokko and her colleagues, including Daniel Rankin, have published a series of papers looking at whether and how a species might evolve itself to death, with selection for individual advantage leading to population collapse. (In a not-very-useful sense, every adaptation beyond being a string of RNA sitting in the primordial soup is a tragedy of the commons, because it diverts resources from reproduction in search of a competitive advantage.)

It's this connection that originally set me thinking about Frank's take on evolution, although, as is the way of these things, nothing of that ended up in the piece.

The main purpose of this post, then, is to make up for that by directing you to this very readable paper published in Oikos early this year, in which Kokko and Katja Heubel draw the link between tragedies of the commons, levels of selection (i.e. individual vs group) and sexual conflict (differing evolutionary interests between males and females).

As an example, they use a fish, the Amazon molly, so called not because of where it lives (Mexico/Texas), but because it's an all-female species. But even though it produces asexually, it still needs to mate with a male of a closely related molly species, to help things along developmentally.

The Amazon molly, then, is a sperm parasite, and the host species would be better off if males could resist the temptation to mate with them. Selection on individual males, however, usually tends towards indiscriminate keenness, because missing out on a genuine mating costs more than mating erroneously. So a tension between group and individual good is created. Can this, Kokko and Heubel ask, lead to prudent males? There's some evidence it can — males from population that coexist with Amazon mollys are choosier than those that don't.

Besides all that cool stuff, another reason I liked this paper is that it says this about the group selection debate:

Our second message is to remind researchers that much of the battle about levels of selection is ultimately about how we teach students about evolution. For some reason, most laymen who accept evolution think of natural selection as something that ensures the survival of a species. Student generation after student generation, bright young minds must be made aware of the flaws lurking in naïve group selection thinking before they can hope to argue clearly about evolution. …The mainstream approach of evolutionary biologists in dealing with this problem is to learn to label all ‘group’ arguments as inherently dodgy.

Given the number of dodgy arguments ever produced, this rule of thumb is often valid. Still, recent theoretical work creates the very valid question by any deeply thinking student: if kin and group selection really are two sides of the same coin, why is one ‘good’ and the other ‘bad’ in our textbooks? The crux of the issue seems to be no particular scientific result, but the fact that for some unknown reason it is much more natural for people to come up with naïve (wrong) group selection arguments than naïve (wrong) kin selection arguments, and evolutionary biologists consequently have to be trained to be very wary of the former. … However, among experts, it might be time to move on from petty semantics to a true appreciation of demographic consequences of cooperation and conflict, and the rich tapestry of evolutionary outcomes that can arise over different time scales, whichever the favoured mathematical method each person chooses to employ.

Which seems a very useful way of looking at it.