An Intrinsic Advantage of Sexual Reproduction

The prevalence of sexual reproduction ("sex") in eukaryotes is an enigma of evolutionary biology. Sex increases genetic variation only tells its long-term superiority in essence. The accumulation of harmful mutations causes an immediate and ubiquitous pressure for organisms. Contrary to the common sense, our theoretical model suggests that reproductive rate can influence initiatively the accumulation of harmful mutations. The interaction of reproductive rate and the integrated harm of mutations causes a critical reproductive rate R*. A population will become irreversibly extinct once the reproductive rate reduces to lower than R*. A sexual population has a R* lower than 1 and an asexual population has a R* higher than 1. The mean reproductive rate of a population reached to the carrying capacity has to reduce to 1. That explains the widespread sex as well as the persistence of facultative and asexual organisms. Computer simulations support significantly our conclusion.