The history of chickens (Gallus domesticus) is a bit of a puzzle. They were first domesticated from a wild form called red junglefowl (Gallus gallus), a bird that still runs wild in most of southeast Asia, likely hybridized with the grey junglefowl (G. sonneratii). That occurred probably about 8,000 years ago. Recent research suggests there may have been multiple origins in distinct areas of South and Southeast Asia, including North and South China, Thailand, Burma and India.
Wild Chickens: The Red Junglefowl
Since the wild progenitor of chickens is still among us, comparisons of behavior and other changes that exist are available to us. Behaviorally, domesticated chickens are less active, have fewer social interactions, are less aggressive to would-be predators, and are less likely to go looking for foreign food sources than their wild ancestors. Other changes include increased adult body weight and simplified plumage; egg production starts earlier, is more frequent, and produces larger eggs.
Genetic studies suggest multiple origins of domestication. The first archaeological evidence to date is from China about 5400 BC, in geographically widespread sites such as Cishan (Heibei province, ca 5300 BC), Beixin (Shandong province, ca 5000 BC), and Xian (Shaanxi province, ca 4300 BC).
Domesticated chickens appear at Mohenjo-Daro in the Indus Valley by about 2000 BC and, from there the chicken spread into Europe and Africa. The earliest firm evidence for chickens in east Africa are illustrations from several sites in New Kingdom Egypt. Chickens arrived in western African at Iron Age sites such as Jenne-Jeno in Mali, Kirikongo in Burkina Faso and Daboya in Ghana by the mid-first millennium AD.
History of Chickens in the Americas
It is believed that chickens were brought to the Polynesian islands from southeast Asia with the Lapita expansion, about 3300 years ago. While it was assumed that they had been brought to the Americas with the Spanish conquistadors, presumably pre-Columbian chickens have been identified at several sites throughout the Americas, most notably at the site of El Arenal-1 in Chile, ca 1350 AD.
Chickens in America, Revisited
A new sequencing of ancient and modern DNA from chickens reported in 2014 (Thomson et al.) identified the likely genetic markers of authentic ancient Polynesian chickens. They assert that among Polynesian chickens, one particular cluster of mitochondrial DNA, Haplogroup D, is the signature of the founding lineage of Polynesian chickens. Haplogroup E is the key piece of genetic evidence supporting the precolumbian presence of Polynesian chickens on the coast of South America: Storey and colleagues pointed to the presence of haplogroup E in both chickens from Rapa Nui (Easter Island) and coastal Chile (El Arenal-1). Thomson and colleagues argue that the presence of Haplogroup E in chickens from Rapa Nui is from contamination.
In supplementary data provided with the Thomson article, the researchers indicate that Haplogroup D closely follows the distribution of cockfighting in India, Indonesia, China and Japan, also a traditional practice in Polynesian societies. In contrast, the other haplogroups, including A, B and E, are ubiquitous world-wide. Radiocarbon dates from el-Arenal and the other early South American sites fall as early as 1350 but are debated in the published literature. This new report puts a serious dent in the precolumbian chicken theory.
Simulations from the Thomson study also indicate that chickens were transported from New Guinea into Micronesia by about 3,850 years ago; and separately from New Guinea to the Solomons, Vanuatu and eastward at a later date.
This article is part of the About.com Guide to the History of Animal Domestication. See page two for a list of references used to write this article.