colin said, about being gay and genetics:
i am hopelessly behind on reading jmdl digests, so i don't know if anyone has responded with what i'm about to say, but...IF it was just down to 'environment', it is highly unlikely that you get more than one in a group of siblings. The biggest hint that is genteic is the fact that are groups of siblings where the incidence of homosexuality is high.
just because there is a high incidence of something in a family is not in any way an indication that something is 'genetic' and not 'environment' (not that there is ever one or the other - there are not only interactions but transactions such that the environment has an impact down to a cellular level...). for instance, three siblings growing up in the same family have the same parents, live in the same house, probably attend the same schools - anything that the siblings have in common could easily be a product of their social relationships and interactions.
similarly, just because depression 'runs in the family' doesn't mean it is genetic, per se. a depressed mother could interact with her family in such a way that the children are more likely to develop depression, and they in turn, as parents, can pass that 'environment' on to their children.
i'm NOT saying that there aren't genetic components to these things. everything is an interaction of our genetic inheritance and our social and cultural worlds. the interesting question is how they influence each other to produce patterns of thought and behavior. BUT my overall point is that looking at siblings raised in a single family will not tell anyone anything about genetics.
people do look at siblings-separated-at-birth, twins raised together and apart, and other sorts of kinship oddities to try and parcel out genetic and environmental contributions to behavior. but a) children raised separately from family members, children who are adopted and children who are twins have very different experiences than children who are singletons and raised with their families (not *worse* just different), and b) the equations behavioral geneticists use to determine the proportion of a trait "due to" genetics or environment are fatally flawed because they do not take into account *any* interaction between a person's genetic inheritance and their environment. and since we know that isn't how it happens, the equations give obviously flawed information that people nonetheless use...
ok, the developmental psychologist gets off the soapbox,
yael
