I would become religious strictly for the benefit of getting laid. Especially if there were a lot of women and no other guys to compete with. +1 if their religion has no problem with promiscuity and sex without marriage (or maybe I could just marry them all.)

Otherwise, I could care less about the survival of the human race. In the grand scheme of things, our survival is meaningless. There is likely intelligent life elsewhere anyways. Once I die, I won't be around care.