Growth, efficiency, and yield of commercial broilers from 1957, 1978, and 2005
Zuidhof, M. J., et al.Poultry Science, 2014DOI: 10.3382/ps.2014-04291
Raised 1957, 1978, and 2005 broiler chicken breeds under identical conditions: the 2005 bird grew to over four times the weight in the same time. The clearest documentation of what selective breeding has done to the animals themselves.