Agriculture began thousands of years ago when early farmers began to raise wild plants and animals for food. Long before genes were discovered and genetics emerged as a field of study, farmers learned to selectively breed individuals for desirable traits (or to avoid breeding for undesirable traits). The process of
resulted in breeds and varieties that are largely dependent on human inputs for their survival.
Subsequently, modern agriculture evolved into the practice of raising
of crops and livestock, in which most of the gene variants (alleles) are the same in every individual of a particular variety or breed. Present-day monocultures are highly productive, but their reduced genetic variability leaves them with a diminished capacity to deal with new diseases, pests, and other changes in environmental conditions.
As the world's population increases and the amount of arable (farmable) land decreases, humans are becoming more dependent on a few highly productive varieties, and on global, rather than local, food production. This greater dependence on varieties with little genetic variability has the potential for worldwide impact, should disease or other environmental change arise.
As farmers and agricultural scientists continue to address the world's ever-increasing food requirements, conservation of genetic diversity will play a pivotal role in the development of new varieties and in meeting new environmental challenges.