Cover image: Pictured is a Beijing Fatty Chicken, a popular domesticated breed in Beijing, China. Hai Xiang et al. compared mitochondrial DNA sequences from 2,300 to 10,500-year-old chicken bones from archaeological sites in China with those from modern ground-feeding birds, including pheasants, rock partridges, and chickens, to investigate the timing and source of chicken domestication. Phylogenetic analysis revealed that the ancient chickens likely contributed to the gene pool of modern chickens, and that northern China may have been one of several sites of chicken domestication in the world. See the article by Xiang et al. on pages 17564–17569. Image courtesy of Huagui Liu (Institute of Animal Husbandry and Veterinary Medicine, Beijing; and Beijing Academy of Agriculture and Forestry Sciences, Beijing).