The molecular basis of the evolution of sex

Traditionally, sexual reproduction has been explained as an adaptation for producing genetic variation through allelic recombination. A recent informational approach has led to the view that the two fundamental aspects of sex—recombination and outcrossing—are adaptive responses to the two major sources of noise in transmitting genetic information—DNA damage and replication errors. This view is referred to as “the repair hypothesis.” In the repair hypothesis, recombination is a process for repairing damaged DNA. In dealing with damage, recombination produces a form of informational noise, allelic recombination, as a by-product. Recombinational repair is the only repair process known that can overcome double-strand damages in DNA, and such damages are common in nature. Recombinational repair is prevalent from the simplest to the most complex organisms. It is effective against many different types of DNA-damaging agents and, in particular, is highly efficient in overcoming double-strand damages.