We evolved thousands, even millions of years before DNA testing. Same as we evolved before cars and planes, antibiotics, mega cities or the interwebs.
And I agree that alloparenting is usually positive. Ever more I'm realizing that Gunner is the closest I will ever be to having a child. And at 15 I can say that she was rather than is. I'm just pointing out why virginity or chastity is more valued in females than males.
Which is also why gays and lesbians tend much more not to care. They know they're not reproducing.