<span>genetic variation in asexual species may have large effects on community and ecosystem functions, increasing their stability, productivity, and species richness.</span>
Normally, members of an average community have downfalls in their DNA. However, as each being is completely different, different imperfections affect different people.
Now, imagine a community based on the offspring of two people. The imperfections passed on through the family line will grow stronger and stronger until a disease rare to normal human life strikes the family.
This is one of the reasons why incest is illegal (although still pretty gross even without that fact.)
