Hybrids between Green Junglefowl Gallus varius and domestic fowl G. gallus domesticus confused several 19th-century ornithologists. The plumage of these hybrids is so unlike the colours and patterns of either of the parent species that they were considered to be distinct species: G. aeneusTemminck, 1825; G. temminckiiGray, 1849; and G. violaceusKelsall, 1891. Darwin wanted to understand if G. aeneus and G. temminckii were hybrids or species, as part of his research on the origin of the domestic chicken. His view was that all domesticated fowl have a single wild ancestor, Red Junglefowl G. gallus (formerly G. bankiva). A hybrid specimen now present in the bird collection of the Natural History Museum at Tring played an important role in Darwin's reasoning and, although the conclusions he drew from this specimen were incorrect, his single-ancestor origin theory for domesticated fowl stands.

‘These hybrids were at one time thought to be specifically distinct, and were named G. aeneus. Mr. Blyth and others believe that the G. Temminckii is a similar hybrid' (Darwin 1868a: 234–235).