Boobies, Blue-footed And OtherwisePublished 5 October, 2011
Suppose someone wrote a paper, which was subsequently covered in the popular press, that proposed a function for some relatively rare but consistently observed behavioral trait in some species. Just because I like blue-footed boobies so much, let’s pick them, and because of its moral overtones, let’s pick something nasty these birds do, siblicide.
So, suppose someone proposed that killing one’s siblings — siblicide — was an adaptation, designed to solve the problem of gathering parental investment at the expense of one’s sibling (a la Trivers), but only when resources were scarce. (By the way, nothing turns on whether this is right or not, and I’ve actually taken liberties here. I’m only interested in how one might react to this line of argument.) That is, the idea is that there is an adaptation among blue footed boobies which is facultative, and that their booby brains are designed in such a way that they try to kill siblings under some conditions but not others. (See this little page aimed at undergrads; or this paper.)
Here is one way some blogger might react to this (bold is my emphasis):
In order for siblicide to have a selective advantage there has to be an important genetic component. Let’s imagine over evolutionary time there were two groups of boobies who differed in their siblicide alleles. One group killed siblings when resources were scarce. The other didn’t. Somehow the siblicidal group managed to have more offspring than the kind group so the allele for not killing kin was eliminated from the population.
Notice the writer has made a mistake. (And I’d like to hold aside, for the moment, the writer’s move here, which implies that the authors think there is one, single, “siblicide gene,” as opposed to a number of genes that have causal effects on the development of the trait.) What gets eliminated from the population is alleles that cause, relative to alternative alleles, not killing kin under particular circumstances. This is a very basic mistake, thinking that the claim of adaptation — surrounding a hypothesized function of a pattern of behavior when it occurs — is a claim that the trait will be seen in every instance of every organism. Many adaptations are, of course, facultative, responding to the environment.
Now suppose our fictitious author continues:
If the scenario is correct then most boobies have to carry the siblicidal allele since it was selected in the past. This seems very strange since most boobies don’t kill their siblings. (The author would then insert a sarcastic footnote, but I’ll just omit that.)
Notice the mistake here. The claim in the original paper is that the function of siblicide has to do with the issue of parental investment, and this adaptation functions by the birds in question being siblicidal under the right circumsatnaces. That is, the claim in the paper is not that all birds will always kill all siblings. (Though this might be the case for the Masked Boobie (pictured above), which might be obligately, rather than facultatively, siblicidal.) The point is that no serious biologist would take the fact that a particular behavior which is posited to have an adaptive function isn’t universal to be evidence against a claim surrounding a facultative adaptation.
Now suppose our hypothetical author said that because this trait, predicted to occur only in certain circumstances was not, in fact, seen all the time, then,well, there is something “seriously wrong” with the field from which the paper is drawn. (In this case, it would be behavioral ecology.)
Now, finally, because the topic at hand is something with moral overtones, let’s say the author punctuated the critique with a pious remark about how siblicide is bad, bad, bad, and that the boobies who engage in it are “assholes,” and added that, hey, we can all overcome our bad, bad traits.
What kind of person would thoroughly botch an argument about a paper, condemn an entire discipline on the basis of the incorrect analysis, and then brandish their moralistic piety by condemning the behavior in question? I don’t know…some kind of Moran?
(Hat tip: Joe P. By the way, obviously I too oppose domestic violence.)