The Flamingo’s Smile by Stephen Jay Gould Read Free Book Online Page A

individuals, as Darwinism argues.
    The scorpion story, despite its citation among best cases, provides no evidence at all. As I read Polis and Farley, I note only that males try their best to escape after copulation and succeed in a great majority of cases (only two failed). Indeed, their mating behavior, both before and after, seems designed to avoid destruction, not to court it. Before, they turn off the female’s aggressive instincts by marching and stroking. After, they hit and run. That a few fail and get eaten reflects the inevitable odds of any dangerous game that must be played.
    Black widow spiders and praying mantises offer more to the theory of direct selection for destruction among males. The spiders seem to be as cautious as scorpions before, but quite lackadaisical after, making little if any attempt to escape from the female’s web. In addition, if the mating plug that they leave in the female debars them from any future patrimony, then they have fully served their Darwinian purpose. As for mantises, the better performance of a headless male might indicate that sex and death have been actively conjoined by selection. Yet, in both these cases, other observations render more than a bit ambiguous any evidence for active selection on males.
    As a major problem for both mantises and spiders, we have no good evidence about the frequency of sexual cannibalism. If it occurred always or even often and if the male clearly stopped and just let it happen, then I would be satisfied that this reasonable phenomenon exists. But if it occurs rarely and represents a simple failure to escape, rather than an active offering, then it is a byproduct of other phenomena, not a selected trait in itself. I can find no quantitative data on the percentage of eating after mating either in nature or even in the more unsatisfactory and artificial conditions of a laboratory.
    For mantises, I find no evidence for the male’s complicity in his demise. Males are cautious beforehand and zealous to escape thereafter. But the female is big and rapacious; she makes no distinction between a smaller mantis and any other moving prey. As for the curious fact of better performance in decapitated males, I simply don’t know. It could be a direct adaptation for combining sex with consumption, but other interpretations fare just as well in our absence of evidence. Hard-wired behavior must be programmed in some way. Perhaps the system of inhibition by a ganglion in the head and activation by one near the tail evolved in an ancestral lineage long before sexual cannibalism ever arose among mantises. Perhaps it was already in place when female mantises evolved their indiscriminate rapacity. It would then be co-opted, not actively selected, for its useful role in sexual cannibalism. After all, the same system works for females too, although their behavior serves no known evolutionary function. Decapitate a female mantis and you also unleash sexual behavior, including egg laying. If one wishes to argue that the system must have been actively evolved because the female tends to eat first just that portion of the male that unleashes sexuality, I reply with a bit of biology at its most basic: heads are in front and females encounter them first as the male approaches.
    The black widow story is also shaky. Males may not try to escape after mating, but is this an active adaptation for consumption or an automatic response to the real adaptation—breaking of the sexual organ and deposition of a mating plug in the female (for such an injury might weaken the male and explain his subsequent lassitude)? Also, male black widows are tiny compared with their mates—only 2 percent or so of the female’s weight. Will such a small meal make enough of a difference? Finally, and most importantly, how often does the female partake of this available meal? If she always ate the exhausted male after mating, I would be more persuaded. But some studies indicate that sexual