Pages

The domestication of chickens

Chicken and humans have conquered the world together. Where humans went, chicken went too. Chicken (Gallus gallus domesticus) were first domesticated some 8,000 years ago from a hybrid of wild red junglefowl (Gallus gallus), and gray junglefowl (Gallus sonneratii).
[Red Junglefowl]
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. Chicken now have increased adult body weight and simplified plumage, while their egg production starts earlier, is more frequent and produces larger eggs.
[Grey junglefowl]
Research suggests there may have been multiple origins in distinct areas of South and Southeast Asia. The earliest archaeological evidence to date is from China about 5400 BC, though a few studies supported even earlier domestication of chicken in northern and central China[1]. Researchers think that chickens were a rare occurrence in northern and Central China, and thus probably an import from southern China or Southeast Asia where evidence of domestication is stronger.

The red junglefowl and gray junglefowl also live in India. Domestication of chickens appears in the Indus Valley around 2000 BC[2]. From there the chicken spread into Europe and Africa. Chickens arrived in the Middle East starting with Iran at 3900 BC, followed by Turkey and Syria (2400-2000 BC) and Jordan by 1200 BC.

The earliest firm evidence for chickens in east Africa are illustrations from several sites in Egypt's New Kingdom. Chickens were introduced into western Africa multiple times, arriving at Iron Age sites in Mali, Burkina Faso and Ghana by the mid-first millennium AD. Chickens arrived in the southern Levant about 2500 BC and reached Iberia in circa 2000 BC.

Chickens were brought to the Polynesian islands from Southeast Asia by Pacific Ocean sailors about 3,300 years ago. While it was previously assumed that they had been brought to the Americas by the Spanish conquistadors, pre-Columbian chickens have been identified at several sites throughout the Americas, most notably in Chile and dated at about 1350 AD.

But there's a problem: some archaeologists argue that the presence of haplogroup E in chickens from Rapa Nui (Easter Island) and coastal Chile must have come from chickens that travelled the Pacific with the Polynesians[3]. Others claim that the presence of haplogroup E in chickens from Rapa Nui is from contamination[4]. If the latter is true, then chickens must have travelled the Atlantic with Columbus.

[1] Xiang et al: Early Holocene chicken domestication in northern China in PNAS -2014
[2] Kanginakudru et al: Genetic evidence from Indian red jungle fowl corroborates multiple domestication of modern day chicken in BMC Evolutionary Biology – 2008
[3] Storey et al: Polynesian chickens in the New World: a detailed application of a commensal approach in Archaeology in Oceania – 2013
[4] Thomson et al: Using ancient DNA to study the origins and dispersal of ancestral Polynesian chickens across the Pacific in PNAS – 2014.

No comments: