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 Danube Delta An interesting ethologic aspect appearing enhanced by the conditions of the Danube Delta (especially by the floods) is represented by egg laying in common nests. Thus, as a consequence of the general lack of egg-laying places, especially at flood time when a great part of the aquatic-species nests are flooded, the birds this way affected go on laying eggs in alien nests either belonging to the same species or to species of the same families. The following up of the tropic regime of the deltaic birds according to its origin had in view to know the food cycles, especially as