Exactly. What you are calling "defective" is homosexual behavior. That's the behavior that you are saying doesn't get passed on. Homosexual, as in attraction to the same sex. As opposed to heterosexual, attraction to the opposite sex. You can't really "imagine" that two male animals are having sex or have bonded to each other. That's a scientific observation -- objective, not subjective. In your own post you admit that it occurs.
How is it possible that you are not able to see this?
Scientific observations by gay scientist???? When there is a politic is involved there is no science