Not to be too naive here, but can their be gay incest? I mean, yes, I understand. But wasn’t the whole prohibition of incest initially put in place because of inbreeding? I mean gay is gay. What difference does it make if you are brothers? Okay, I have to go take a shower now...
I don’t think the prohibition against incest is just about birth defects. Even in siblings it’s still not that common.
No it’s not just inbreeding - not by a long shot. Sex is for reproduction, but it is also a powerful reinforcement for a permanent, monogamous relationship.
That’s why, in strong cultures, casual or gratuitous sex is prohibited, and sex is reserved for marriage.
Unmarried people were chaperoned at all times, and all social interaction where sex might occur were monitored carefully.
That’s where taboos against homosexuality and incest entered the picture. Dating and courting between unmarried males and females was watched carefully, but same sex interaction and interaction between family members was impossible to monitor for obvious reasons.
Taboos were needed to discourage that.
The social stigma or punishments for homosexuality or incest were so devastating that they served as a strong deterrent.
Now, that the taboos against perversion are no longer in effect, the whole world is shot to hell.