On Mechanisms and Behavior (was: Re: Adaptationism again)

Bryant (mycol1@unm.edu)
13 Sep 1996 14:01:20 -0600

In article <51br2c$n2m@panix2.panix.com>, Paul Gallagher <pcg@panix.com> wrote:
>The burden of proof is on the sociobiologist to prove that jealousy, or any
>aspect of human behavior or culture, can be usefully or meaningfully considered
>to be a genetic trait. Once you have done that, we can talk about the role of
>selection in forming the trait.

The burden of proof is no greater for sociobiologists than it is for any
other science. Meaningful heritability studies progressed long before
molecular genetics. But let's explore the logical conclusions to be
drawn from the position you articulate above.

Your arguments suffer mightily from what evolutionary psychologists call the
"Situational Error." All behavior results from mechanisms in the
behaving organism. Environmental inputs activate those mechanisms.

To quote Buss, "No behavior can be produced in the absence of mechanisms.
There is no such thing as a purely environmental or situational cause of
behavior" (Buss 1991).

Different species do not respond identically to identical environmental
stimuli, even as unencultrated juveniles, after all. Nobody reasonably
expects that transplanting a sparrow embryo's brain into a human embryo
would result in the development of a normal human brain. Genetic
contributions to brain are inescapably real. Those genetic contributions
need not necessarily explain individual differences within a species,
since adaptations are expected to be driven by selection to fixation--in
other words, to be present in every member of a species, given enough
time and strong enough selection pressure. (Hence, evolutionary
psychologists are looking at traits which emerged before ancestral asians
and europeans left Africa--looking, in other words, at species-typical
traits. Dont' mistake us for behavior geneticists!)

So what we have here is adaptationist psychologists positing that the
brain is a collection of task-specific information processing,
behavior producing mechanisms, and critics like you (apparently) proposing a
general-purpose computing model of brain, with no learning or functional
biases, just sitting there, tabula rasa, waiting for culture
("superorganic" culture, no doubt) to come scribble on it.

At the very least, you surely must concede that there's *some* kind of
learning mechanism in place, no? Operant conditioning mechanisms, perhaps?

Are we to conclude that until you establish the exact molecular genetic
nature of such a mechanism, you are unable to begin to account for any
behavior at all?

That's the logical conclusion of your assertions, quoted above.

I prefer the scientific approach of allowing you to test the predictions
derived from your hypothesis, even if that hypothesis is based on an
assumption that the trait in question was once heritable. If you're
wrong, your falsifiable predictions will, after all, be falsified.


Buss, 1991. Evolutionary personality psychology. Ann. Review of
Psychology, 42: 459-491.