Thank you frogprince... saves me the trouble of posting similar quotes.

There are many studies linking genetics to sexual preference. What GfS and Ake seem to be demanding is something like "visible, direct causality", which is very seldom available in these issues.
Think about this: we KNOW that dogs can be bred for traits like aggressiveness and docility, without knowing the precise chromosomes where the relevant changes are located. We know that many, many traits in both humans and 'lower' animals are determined genetically... so why not sexuality? You don't accept this because it doesn't jibe with your pre-digested opinion(s).