quote:
how do you account for the emotion of "love" going beyond rational and even into behavior that compromises an individuals fitness, in the terms of what Mr. Darwin taught us? I'm talking things like homosexual love or people risking their life to save a pet because they "love" it. If love is simply biochemical, shouldn't natural selection eliminate these types of behaviors from the population?

I explain that by saying that we didn't evolve as individuals. We evolved in social groups.

So, an individual risking his life to save other members is good for the whole group. Even if that person dies, he's helping to save others in the group. Since these groups were small, family groups, they shared much of the same DNA. So, most likely, the individuals that are saved also carry the same traits that make them prone to this savior behavior. Therefore, as Mr. Darwin taught us, the traits that were most advantageous to survival (for the group, not the necessarily the individual) carried on.

All that said, there are many traits that are not necessarily always best. They may be best in some cases, but fail in others. For example, having the instinct to protect offspring from a jackal is almost certainly driven by the same trait/dna as having the desire to protect offspring from a pride of lions. So, while it may be terribly disadvantageous in some cases, if that individual comes across more hungry jackals than lions, overall, it's still a trait that benefits survival of the species.