genetic variance is a concept outlined by the english biologist and statistician ronald fisher in his fundamental theorem of natural selection which he outlined in his 1930 book "the genetical theory of natural selection" which postulates that the rate of change of biological fitness can be calculated by the genetic variance of the fitness itself. fisher tried to give a statistical formula about how the change of fitness in a population can be attributed to changes in the allele frequency. fisher made no restrictive assumptions in his formula concerning fitness parameters, mate choices or the number of alleles and loci involved.