Fisher Contra Zahavi

One of the great debates in evolutionary biology was over whether there could be such a thing as runaway selection processes, or whether apparently daft results of sexual selection nevertheless made evolutionary sense. The classic case was the Argus Pheasant, a species in which the females fancy males in proportion to the length of their tails. In consequence, each new generation was bred disproportionately from the longest-tailed males, and so the length of the tails kept increasing. The point was reached at which the male was too cumbersome actually to fly, but that did not stop the process; for it does not matter whether the resplendent and flightless male gets eaten by the fox or not, provided that he has reproduced first. From the female’s point of view, the point is not only to breed, but to have children who will also breed. This means having good-looking children. The best way to have good-looking children is to breed with someone good-looking. Bucking the trend in long tails would mean that she has sons who will lack the sexy ornaments and therefore be a reproductive dead-end.

When we call this phenomenon “runaway” selection, as if the reproductive processes were a driverless train or a melting-down nuclear reactor, this reflects the value-judgement of the bemused biologist, namely that something is happening that “ought” not to. And yet such a judgment can only be made on the basis of a sentimental identification with the male pheasant that is paying for his success with an early death. It is not, however, certain that an intelligent pheasant would see it that way; after all, many humans prefer to “live fast and die young”. Or perhaps there is some Puritanism involved, whereby we condemn the females for their “superficiality” in preferring long tails, even if it seems to us to mess up the whole species. Runaway selection of this kind is clearly of relevance to our own reproduction as well; the equivalent of the Argus Pheasant and his unwieldy tail may be the insistence of human females on rewarding flashy seducers and strutting hoodlums, however useless and even dangerous they may be in all functions other than attracting women.

The idea that evolution can make such a “mistake” has been vigorously opposed, however, by another school, which asserts that apparently silly external qualities are reliably correlated with valuable genetic traits. It is rational for the females to breed with the possessors of such traits. If the traits are a handicap, well, the whole purpose of a handicap in golf is to allow the expert to demonstrate his superiority; and so too in the case of sexual display. The pheasant that can lug a huge tail around and nevertheless survive is clearly a very strong pheasant, and it makes perfect sense to breed from a specimen so superior that he can overcome this “Zahavi Handicap”. The “Goodgenes” school holds that some qualities simply cannot be faked. For example, the croak of the frog and the roar of the stag are a strict function of size, so that “what you hear is what you get”. If the mating criterion is being able to jump your own height or lug a huge tail around, either a male can hack it or he can’t, with no middle ground.

Yet again, it appears that some animal mating displays function in this way, while others do not correlate with health and are the arbitrary result of the imperative to breed from whatever is considered attractive by your peers. A third factor maybe innate biases in female sensory apparatus, that males have evolved to exploit. Richard Dawkins has thrown yet another spanner into the whole works by pointing out that human advertising is not about honest information, and why should animal advertising not be an attempt at neural subversion too. Finally, it has been argued that all these mechanisms can operate at the same time, in reciprocal interaction, and that mating behaviour is the product of any or all of them at once.

Posted on July 10, 2009 at 11:03 by Hugo Grinebiter · Permalink
In: BEAUTY AND THE BEAST, The Myth Of "Inner Beauty"

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