Animal genetic resources for food and agriculture crop and livestock species in the early neolithic time period changed our human evolution and lifestyles. This ability to control food production led to major demographic, technological, political and military changes. Consecutively, thousands of years of natural and human selection, genetic drift, inbreeding, and crossbreeding have contributed to the diversification of animal genetic resources and increased the variety of environments and production systems that livestock keeping takes place. Relatively few species have been domesticated; out of the world's 148 non-carnivorous species weighing more than 45 kg, only 15 have been successfully domesticated. The proportion of domesticated birds used for food
Birds of the Amazon birds that breed in the northern and southern hemisphere but migrate to the Amazon rainforest for food and shelter that are not available at their breeding places during cold months. Migrating birds greatly rely on rainforests for food, rest and recovery after their dangerous migration during which they can lose 30% of their body weight. Since the 1970s, cattle pasture has been the leading cause of deforestation in the Brazilian Amazon. Land is often cleared for investment purposes due to pastureland prices exceeding forest land prices. In this case, large amounts of forest are torn down and replaced with savanna