Why There Are Two Sexes

One big problem I see with sexual reproduction ever happening would be that two of the same species in the same location would have to "evolve" to have the ability to reproduce sexually. Then those two would have to meet, fall in love (ha ha), and reproduce. Then their "children" must stay in the same general area and repeat the process. This seems to be extremely unlikely to me. It seems far more likely that anything that developed the ability to reproduce sexually would find that trait to be negative in the fight for survival, and it would die out.

If you had all asexual reproducing things swimming around. Developing the needed parts for sexual reproduction would take quite a few "random mutations", none of which would have a beneficial side effect until the point where they were fully developed. They would still have no benefit until another of the same species also developed the sex parts, only opposite (female or male).According to Natural Selection, the sexual parts that started to develop would, for many many generations, give no benefit.these seem like some relatively complex "random mutations" to happen to one member of a species. Then mutate again into the opposite sex, either another member of the species, or one of the descendants of the original guy that got the then useless sex parts.The fact that there are species with both sexual and asexual reproduction does nothing to prove sex evolved. Call me when we can find a species that reproduces via asexual reproduction only starts reproducing sexually.

First of all, I did not mean penis and vagina when I said needed parts. I was talking about whatever parts that were needed for sexual reproduction. In the frogs/fish you mention it would be the parts that make the sperm/egg. For the microbes you mentioned it would be whatever change was required to allow for the other microbe to fuse into it in order to reproduce.I am not a professor of microbiology but I assume there was a change to the microbe that allowed it to combine with another microbe. Now apply my previous points about two microbes needing to develop these changes and all that.