I would tend to think its completely cultural. Look at western Europe from to the fall of Rome to 1900 and you would never assume there was correlation between homosexuality and R1b more than any Haplogroup or place on the planet.
Yet only a couple centuries prior the fall of Rome Plato was writing in the Republic one of the most important books ever written about the temptation to lust after young male pupils and only a few decades after 1900 many western European nations had allowed for same sex marriage.
I believe its just modern "liberal" beliefs and ancient indo european beliefs somewhat overlapping on that one issue. Christianity dominated the cultural attitude toward homosexuality in europe for many years and had been itself influenced by early Semitic views on it(which may have arisen due to cleanliness i.e preventing the spread of STD and then became infused with religious doctrine later on). With rise of Islam in Europe we may even see this happen again as attitudes about homosexuality shift back to another cultural source. What I'm trying to show here is that the trend is transient due to the culture of the time.
It seems in ancient times homosexuality was really a cultural event among warrior peoples or warrior classes, we see it in the Samurai who have nothing to do with Indo Europeans. It was most likely a cultural phenomenon shared among warrior classes or peoples because of their lack of contact with women and strong bond forming with other men. Other cultures may have developed differently and seen it as uncleanly as I described before with Semitic groups, the decision whether to accept it or not probably depended on the cultures environment and which option had the less detrimental consequence.
I may have given the wrong impression about the arguments presented here.
The author isn't saying that male homosexuality was only present in Indo-European societies. He's saying that it was ritualized as a right of passage for adolescent boys in these warrior cultures whether Greek, Celtic, Germanic, Indo-Iranian etc. He even finds it in warrior cultures of Melanesia, so it isn't only
Indo-European warrior cultures.
He also shows that it was present in the prior "Neolithic" cultures.
https://books.google.com/books?id=1...exuality in ancient farming cultures&f=false
I think there's pretty abundant evidence from Canaanite culture that it was ritualized in a completely different context there, as there were male prostitutes in the temples as well as the more common female ones. The male priests took the passive role. So, I don't think there was a "Semitic" or Near Eastern proscription against it. The proscription was the product specifically of Hebrew religious and societal norms. They railed against male prostitution as well as female prostitution in the temples and orgiastic rites of any kind. Even masturbation was a grave transgression, so I don't think it was totally about disease avoidance. It might perhaps have partly been a way to distinguish themselves from the Canaanites whom they wished to supplant, although they took it further than the Indo-Europeans.
http://epistle.us/hbarticles/neareast.html
The literature on the subject is ambiguous, but it does seem there is a genetic component, as well as perhaps epi-genetic factors. It also seems to pass through mothers, not fathers, which would mean that the ychromosome is either irrelevant or a minor factor. That makes sense to me since we can see it is present in cultures carrying diverse yhaplogroups.
That isn't to say that it is not more prevalent in certain ethnicities. I don't think anyone knows that yet, but it may well be true.
Oh, and just because it was a right of passage in certain cultures doesn't mean that most men continued to practice it, because there are indications from ancient literature that this wasn't the case.
