Kolkata: A collaborative study executed by the Scientists of Zoological Survey of India through DNA sequencing of 863 genomes covering all the four species of the genus Gallus, five sub-species of Red Junglefowl (RJF) and various domestic chicken breeds collected worldwide has provided path breaking insights in the understanding of origin and domestication of chickens.
The research assumes significance as despite the substantial role played by chickens in human societies across the world, both the geographic and temporal origins of their domestication remain controversial.
Noteworthy, the epochal work of Darwin postulated that chickens were domesticated around ∼4,000 years B.C. from a single ancestor, red jungle fowl (Gallus gallus gallus) in the Indus Valley. After this, there have been several studies in favour of arguing the concept of monophyletic origin of chicken. But none of them could infer the spatiotemporal origins and genetic adaptations underlying the domestication of domestic chickens.
The research conducted by Dr Mukesh Thakur, Scientist at ZSI in collaboration of Kunming Institute of Zoology, Kunming, China, has revealed that domestic chickens were initially derived from the subspecies RJF- Gallus gallus spadiceus with the epicentre of domestication predominantly located in southwestern China, northern Thailand and Myanmar.
The study proves that following their domestication, chickens were translocated across Southeast and South Asia where they interbred locally with both RJF subspecies and other jungle fowl species. The results further reveal that domestic chickens undergo genetic adaptations that underlie their unique behavioural, morphological and reproductive traits. "Our study provides novel insights into the evolutionary history of domestic chickens and a valuable resource to facilitate ongoing genetic and functional investigations of the world's most numerous domestic animal, " said Thakur.
Relative to other domestic animals including sheep, cattle and pigs, chickens are currently both the preferred source of animal protein and the most numerous domestic animal. The identification of unique genomic landscapes of all RJF subspecies and three additional jungle fowl species suggest that conservation efforts should be made to safeguard them from extinction. The research has been published in Cell Research journal
Dr Kailash Chandra, Director ZSI has raised his concern that indigenous, backyard chickens have been hit badly by several new, emerging diseases, like avian flu, which in turn has led to the ban of chicken keeping by smallholder farmers and the closure of traditional living chicken markets in many countries. "The study may aid to identify the natural adaptation and finding a cure in the poultry diseases," he added.