Males as cheap experimental material
Most of the males in the population can die without any detriment to the reproductive potential of the population. The relatively “cheap price” of male individuals allows males and females to divide some evolutionary roles between them. Females usually take on the function of a conservative agent, whose role lies in transferring tried-and-true traits acquired during evolution from one generation to the next, while males can act as cheap experimental material on which nature can “try out” evolutionary novelties.
Experimental data related to various animal species indicate that the intraspecies variability of males is usually much greater than the intraspecies variability of females. Similar differences also exist in the death rates as a consequence of congenital deformities in embryos and adult individuals of the male and female sex. This phenomenon can be caused by epigenetic mechanisms valid during ontogenesis. However, in most cases, experimental results have unambiguously demonstrated that a greater number of mutations occur in males than in females. It has, for example, been found that, of 33 new mutations in the gene responsible for the formation of retinoblastoma, 31 were located on the chromosomes derived from fathers and only 2 on chromosomes derived from mothers (Kato et al. 1994). The actual mechanism causing elevated frequency of mutations in males is currently not known; however, this could be connected with the increased number of cell divisions occurring in the formation of male sex cells compared to the number of divisions occurring during the formation of female sex cells (Chang & Li 1995; Drost & Lee 1995; Lessells 1997). However, it can also be imagined that the male organism can, for example, turn off some processes of DNA reparation in the germinal line (Huttley et al. 2000).