hen/chicken breeds domesticated versions of the species Gallus domesticus. Their wild ancestors are thought to be several species of jungle fowl, of the same genus, native to the Indian subcontinent and SE Asia. Remains from Chinese sites indicate that the birds could have been domesticated as early as the 2nd millennium bc. However, their diffusion westwards was a long process. They probably reached Britain, for example, with Celtic tribes during the 1st century bc. They had arrived in Greece, probably from Persia, about 500 years before that, and there are numerous references in classical literature, for example to their being served as food at symposia.