In most populations of animals, or higher plants, mobility is restricted. Consequently, mating between individuals of such populations is far from random, this being affected among individuals occurring in proximity with each other in space. Many small sub-gene pools are thus formed within a gene pool. These sub-gene pools depart to some extent, from overall characteristics of the entire pool. One of the consequences of restriction in population size due to restricted mobilities is mating between relatives, which is also called 'inbreeding'. Inbreeding, though, has very little influence on change in overall gene frequencies, has major effects on frequency of homozygotes, which is increased. If a recessive gene is rare, it will appear in homozygous condition at a higher frequency under inbreeding than under random mating. As a result, selection will be provided with increased opportunity to act upon rare recessives. Inbreeding, however, has been associated with unfavourable biological effects, and crossing with an unrelated stock results in increased vigour. This may perhaps be the reason why consanguineous marriages, (marriages between close relatives) have been forbidden. The consequences of inbreeding may, therefore, have wide implications for both natural and artificial selections.