Bonobo chimps regularly engage in sexual relations with each other. They are in fact very promiscuous and have relations with the whole troop just about every day, and they don't stick to the opposite sex. Here is a passage from the Wikipedia article on Bonobos:
Sexual activity happens within the immediate family as well as outside it, and often involves adults and children. Bonobos do not form permanent relationships with individual partners. They also do not seem to discriminate in their sexual behavior by gender or age, with the possible exception of sexual intercourse between mothers and their adult sons; some observers believe these pairings are taboo. When Bonobos come upon a new food source or feeding ground, the increased excitement will usually lead to communal sexual activity, presumably decreasing tension and allowing for peaceful feeding.
It's pretty clear that if they don't have faith that Christ was brutalized on the cross by God as a sin-payment, then God will not forgive them for their evil, and will instead direct his retribution at them. God does not overlook sexual sin -- not even the sin perpetrated by chimps.