Why is it not favorable for all life forms to be Hermaphrodites? ?

Question

I think that having two working sets of s*x organs to either pass on DNA or receive DNA gives a species twice as many chances to reproduce. Why do we see this so rarely in Nature? Would not our own species, Humans, have twice the number of chances to reproduce if we were all Hermaphrodites? I am referring to the ability to create and distribute sperm and create and womb an egg until conception equally. I know this case has never been reported in a human but I do know there was one bird found to have both a working egg and a working t******e. It seems like this would be the logical evolutionary step. Why do we not see this everywhere in nature?

Answer 1

Aggression, pure and simple.

Researchers studying hermaphrodite species of worm at the site below noted that nearly *all* mating in these worm species resulted in injury to the worm carrying fertilized eggs.  Just search the whole phrases "hermaphrodite worms" and "mating violence", quotes and all, at the site below:

http://www.sciencenews.org/

The point of the research is, when everyone in a given species is *Male*, everyone ends up being aggressive and wanting to be the *father* of offspring and not the mother.  This results in mating often if not universally occurring by force--an assault--that injures the "mother" in the situation.

My humble guess on this is that it becomes pro-survival rather quickly to have a less violent system in place that doesn't maim and kill the egg-bearer after *one* mating.

But hey, what do I know?  Those are worms.  But vertebrates can be really aggressive about mating rights too, even without everyone being male.

Answer 2

Becasue it's important to have variance.

It means that the best of two people can come together to create an even better person.

Breeding, Look up Darwin's survival of the fittest.