Question: Why do we not have reproductive systems that can fertilize themselves?

Sean Murphy answered on 22 Mar 2012:

Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only.

Organisms that reproduce through asexual reproduction tend to grow in number exponentially. However, because they rely on mutation for variations in their DNA, all members of the species have similar vulnerabilities. Organisms that reproduce sexually yield a smaller number of offspring, but the large amount of variation in their genes makes them less susceptible to disease. Both methods can be evolutionarily successful depending on the environment and circumstances.