Jgnat
I'm not aware that Steven Pinker ever linked the "ewww factor" with incest; if he did, I would stand corrected. Rather, he focused on human reactions to physiological items (feces, urine, blood, pus ... ) and rot. Interestingly, other studies concluded that children of up to 3 years old don't seem to be "hardwired" at all in this manner. Only when they start to clearly understand what their parents tell them to eat/don't eat or touch/don't touch, is when they develop the "ewww factor" and some other religious-based cognitions, such as "kosher food". Thus, even the "ewww factor", as universal as it may be, appears to have both cultural and biological causes, likely a combination of both, but where the cultural wheighs in more.
Eden