Sex: Advantage

One of the most important unanswered questions in evolutionary biology is why sexual reproduction is so common. In theory, sex is so costly that individuals that reproduce sexually should be at a major disadvantage relative to asexually reproducing competitors. This leads to the expectation that sex should lose in competition with asexual reproduction and thus be rare in nature, which is in striking contrast to its widespread occurrence. It is this profound disconnect between theory and reality that has motivated decades of research into potential advantages of sexual reproduction. While much progress has come from these efforts, why sex predominates is still unclear. It is likely that part of the answer is linked to an advantage of sex under pressure from coevolving parasites. Other important processes may be more efficient clearance of deleterious mutations and other costs associated with asexuality that are not direct consequences of the lack of recombination.