Fables of Cyberspace: Tapeworms, Horses, and Mountains

Abstract

If microevolution is hill-climbing, then macroevolution is valley-crossing leading to higher hills. Does sexuality, making reproduction a reticulate process instead of bifurcating, help macroevolution? Even without valleys, if a niche AB exists but cannot be accessed until either niche A or niche B is conquered, it may appear that sexuals should reach AB sooner because discoveries made by selection in A and B separately can be brought together by recombination: in contrast under asexuality the route to AB has to be either through A or through B, not both at once, and should take more time. Moreover, if valleys on the adaptive surface exist, the force of this presumption is increased. Depending on size of population and depth of valleys, a higher hill may not be accessible by adaptation at all; but with sexuality present at least the chance of attaining the high hill’s slope seems inevitably greater. All this, however, leaves out many potentially relevant factors including the intrinsic inefficiency of sexual reproduction. The last makes sex a strongly inferior competitor to asex in the short term as well as making it (advantageously?) slower to climb slopes once they are found.