1. I should have read more carefully. Yes, I see now that it was Collins who used the 20% concordance for twins. (I believe the most reputable studies have placed those MZ twin concordance rates at 25%-30%.)

However, my point about Bailey is that he speaks of “heritability”–and I still wonder how or if they have actually established that twin concordance rates for SSA (whatever those rates are ) are evidence of genetic heritability as opposed to biological factors. (Again, perhaps the Sanders/Bailey gene study will help clarify this.) That was the crux of my question.

2. Thanks for the link. I should have mentioned that I did know the results of the study. It has been criticized for its sample (internet responders) and as not really establishing much but praised as offering an interesting line of inquiry for further study.

There have been many who have suggested HLA typing might tell researchers something. I guess that is very expensive? Since Bailey’s major research subject seems to be the etiology of SSA, I wondered if he or Sanders (or anyone else with whom they collaborated) had done blood or HLA tests.

I think this huge DNA study Sanders/Bailey got money for only asked for cheek swabs to collect DNA. Unfortunately, if that is the case, it seems they wasted a great chance for other tests. Yes, I suppose they were limited by money. If they get another grant, they might be able to use the same test subjects for further tests.

WOW! Play into stereotypes much at all?

Pretty much every gay man I know loves football!

Maybe they love football players, I don’t know, but there should be a proportion who actually are into sports. Usually, their interests are in the arts, fashion, body care or intellectual area.

Pretty much every gay man I know loves football! Your theories and ideas simply don’t mesh with anything I’ve observed in reality.

Many men who are predominantly SSA report having been taunted and rejected as kids, for instance for not playing football. But I suspect, in some, stressful events wouldn’t be so obvious and therefore they wouldn’t be recalled in connection with sexual identity development (childhood trauma can pass unnoticed or not remembered). What I’m saying is that vulnerable kids go through stressful events or aggressive environments differently than the rest. This might be primarily because of their genetic/hormonal background, but I wonder how much of their adult orientation is a result of them being rejected and growing up apart from their more typical peers. The brain is very plastic at that age and many factors could influence its development. The case of identical twins discordant for sex atypicality sticks out, either as a product of different womb hormones exposure or unique post-natal factors. It’s the unique factors that might be more important for boys who grow up in a typical way, but end up attracted to their own gender in adult age. That was your question, right?