[QUOTE=ITR champion]
There is something exceptional about reason, namely that it can trump any other influence on our thinking and behavior. Even if it’s an ability we evolved, it’s in a class by itself.
[/QUOTE]
I don’t think you can make a clear-cut distinction like that. Take fear, panic, for instance: I guarantee you that if put under enough emotional stress, no amount of reasoning will be able to compete with your basic survival instincts. There was a recent threat here about waterboarding, that showed this pretty clearly: despite not being in actual danger, and even in control of the situation, the poster (Scylla) was unable to overcome his reaction to the drowning sensation, and that’s how waterboarding works (and, essentially, the same reasoning works for other base instincts, though maybe less clearly so. There’s plenty of examples of people having woken up the next morning with a lot of regrets, which you wouldn’t have if your decisions of the night before had been entirely rational and not influenced by a hard-wired desire to mate).
I’d say that to deny an evolutionary influence on our decisions is to deny a biological component in them, since our biology is definitely a product of evolution, and there’s ample evidence that the current state of our biology, of our hormones, neurotransmitters and whatever else creeps through our cells does have an influence, that there is a chemical basis for at least some percentage of influence on how we react in a given situation. That might not determine us entirely, but noone’s talking about that – take your earlier example of making a decision between chastity, monogamy and polygamy: obviously, you can’t decide for 60 percent monogamy, 40 percent polygamy, but your genetic predispositions might give your decision for monogamy a 60 percent probability.
Still, though, I do think that EP is a bit too simplistic a picture; as Mangetout already pointed out, evolution (or rather, natural selection) isn’t confined to genes, particularly in the human case, because we have developed other methods to hand down information to our successors, like oral tradition, writing, and, in recent times, direct audiovisual recordings. Susan Blackmore claims that there are two separate (but interconnected) evolutionary mechanisms working in an intelligent, conscious species, a genetic and a memetic one, which she uses to explain our super-sized brains; I’m not sure if even that is the complete picture, but I do think it’s essentially the right starting point.
Thus, it’s not just the evolution of our genes that puts a predisposition on our decision-making process, but that of every bit of (imperfectly) hereditary information that accretes to form our culture, our society, and our mores.