Genetic drift is the random change in the genetic composition of a population to chance events causing unequal participation of individuals in producing succeeding generations.

Along with natural selection, genetic drift is a principal force in evolution. It occurs in populations of any size, however, is most effective in small populations; when populations are cut in size dramatically through natural disasters or isolation, genetic drift has major effects. 

It may result in the loss of some alleles that may even be beneficial to the organism and fixates on other alleles. Due to not all beneficial alleles being preserved by this form of adaption, genetic drift varies from natural selection. This is due to ineffective or even harmful alleles possibly becoming fixed within a population, purely by chance; natural selection, on the other hand, allows the survival of the most efficient alleles to be passed on through generations, this allows harmful or ineffective alleles to be removed from the population. 

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