>>16788314
Nothing. The spectrum of human sexuality is naturally broad, with most humans being bisexual to some degree as the norm. Otherwise, homosexuals would have already become extinct, as sexuality is fundamental to reproduction and genetic transmission. Now, if you're wondering why bisexuality and not heterosexuality, I'd say it's probably related to group bonding. Primates are among the most social mammals. Primates' highly social behavior is widely considered a key driver of the evolution of their intelligence.