Monte Carlo Simulations of Sexual Reproduction
  Modifying the Redfield model of sexual reproduction and the Penna model of biological aging, we compare reproduction with and without recombination in age-structured populations. In contrast to Redfield and in agreement with Bernardes we find sexual reproduction to be preferred to asexual one. In particular, the presence of old but still reproducing males helps the survival of younger females beyond their reproductive age. 
D. Stauffer, P.M.C. de Oliveira, S.M. Moss de Oliveira and R.M.   Zorzenon dos Santos