The number of breeds of domesticated animals, especially livestock, have declined rapidly. The proximate causes and processes involved in loss of breeds are outlined. The path-dependent effect and Swanson’s dominance-effect are discussed in relation to breed selection. While these help to explain genetic erosion, they need to be supplemented to provide a further explanation of biodiversity loss. It is shown that the extension of markets and economic globalisation have contributed significantly to genetic loss of breeds. In addition, the decoupling of animal husbandry from surrounding natural environmental conditions is further eroding the stock of genetic resources, particularly industrialised intensive animal husbandry. Recent trends in animal husbandry raise very serious sustainability issues, apart from animal welfare concerns.