I think it might be the case that there is partly a biological basis for the incest taboo, but I'm not sure, I don't know. I think I've provided a fairly good account of how this might occur. You on the other hand seem to be utterly convinced of whatever it is that you believe to the exclusion of even considering anything else as being reasonable. I haven't asked for it because I'm not arguing but where is your coherent water-tight argument that biology absolutely plays no part whatsoever in being the basis for the incest taboo?
What is the mechanism by which biology has created the incest taboo? Thanks in advance for your answer.
I don't know if you realize this, but most evolutionary biologists believe that there's a biological incentive/imperative for all people to have sex with as many partners as possible in order to ensure that they have as many offspring as possible. Doesn't matter if they're your cousin, or whoever. Look at dogs, look at monkeys--a male monkey or dog will fuck another male dog, or a female monkey who's in heat (usually not one who isn't)...a person's leg...a teddybear...In this view, people are wired to have as much sex as possible with whomever is handy so that the chances are higher that people will reproduce.
I tend to disagree with this view, because I believe there's a biological incentive to hedge one's bets when it comes to reproduction. One child who is adequately taken care off and who will "thrive" and produce its own offspring is preferable to three who can't be cared for (fed, sheltered, educated to work, socialized to be decent to others and sociable, etc.) and who will be more likely to die without reproducing. Given human babies need more one-on-one care from their mother than any other species' offspring, and more investment of time/resources/psychological interest, it seems that being selective about reproductive partners would have higher pay offs than indiscriminate fucking and impregnating, in terms of conferring advantages to one's offspring that will ensure that they will in turn successfully reproduce. As a male, you don't want to waste your time fucking, say, a terrible alcoholic who is going to miscarry or who won't take care of the kid even if it's born. Even if she looks good and you're attracted to her. So you might have sex, receive some measure of sexual satisfaction from her, because she's handy, but you'll use a condom and wait until a more suitable parent comes along. Maybe she gives you everything your mother didn't--love, stability, emotional support. As a woman, there's no biological incentive to fuck a gorgeous man if he's homeless and won't be able to help contribute some money or resources to ensure the kid is healthy and thrives (at least in situations where a woman herself does not have the resources to provide for the child alone). But it might feel really good and maybe you'd need it right then for whatever reason.
Another example: There's no biological imperative for rape, because in the ancient past we know most women left babies who were the product of rape out in the woods to die. (Hell, they left all kinds of babies in the woods to die--infanticide was commonplace before abortion was accessible and safe.) There's no point in producing offspring that won't make it to reproduce themselves. Or in even trying. This is a waste of time and precious resources. But there could be a psychological reason, and a basic physical reason (I'm horny and x is willing), to have sex with someone who might not be a great parent.
In other words, there many reasons why we fuck, and often reproduction has nothing to do with them--they're the same reasons why we piss when our bladder spasms, or why we go out and drink with friends. Because we need relief or an outlet for other psychological needs that are just as hard-wired as "hey orgasms feel good" is. I think evolutionary biologists ignore this sort of incidental/psychological fucking when they try to explain how we came to be what we are, and all too often evolutionary biology is used to explain what people *already think they know* about people (e.g. men are promiscuous, women are monogamy robots, etc) without first challenging these assumptions. (Just like the "orgasmatron" scientists ignore the fact that female orgasms are not achieved solely through mechanical stimulation and identical across the sex, unlike male orgasms which are...)
The problem with trying to assume that we know which cultural values are biologically based is that evolution is a dynamic process, where many many factors (environmental ones that we have no idea about, for one) worked in combinations we can never replicate and entirely random genetic mutations were, thanks to specific environmental cues, advantageous for some people and therefore those people were more likely to survive and reproduce more healthy offspring, (and thereby exert a larger influence over the gene pool), and so on...
Not something we'll ever be able to adequately model in a lab/research setting.