Question: How come all species have male and female.. but nothing else. All or most species have males and females but some don't... do you think humans will evolve so they are both male and female so they can give birth but they have their own sperm inside? Thanks for taking the time to answer this - hope you win! :) Sarah x

Ceri Brenner answered on 24 Jun 2011:

So I’ve been thinking about this one, and although I’m no expert, I think this has to do with the need to mix genes in order to produce strong and healthy offspring and that the best way to do this is to have two carriers of the two reproductive cells. I think by having male and female (or sperm and egg if you don’t want to be called male and female), this means that we need to find a mate in order to reproduce and so therefore the gene pool is naturally enhanced. It is to the benefit of the human race that we mix genes in order to keep us a strong, healthy and intelligent species. To have more than two genders might mean that the gene pool would be reduced eventually and this would be a bad thing for our species. Humans have been evolving for many many years, and I think if it was our destiny to have more than one gender, then it would have happened by now.