Discovery Gives Researcher Something to Crow About : Science: Genetic typing shows poultry was first bred for food about 10,000 years ago in Vietnam, much earlier than previously thought.
In a scientific “coop” that appears to have tracked down the Adam and Eve of poultry, researchers at the City of Hope Medical Center have found that the modern poultry industry got its start more than 10,000 years ago when a Vietnamese farmer took a pair of red junglefowl into his hut and began breeding them.
All domesticated chickens now grown in the world--an average of more than 8 billion a year--are descendants of those unlikely ancestors, which still exist in their ancient form, according to genetic typing results reported this month in the Proceedings of the National Academy of Sciences.
The discovery moves the date for domestication of fowl back at least 2,500 years and shifts the site of the event south from the steppes of China, where archeologists had previously found the remains of what may have been the first takeout chicken.
“That’s much older than anyone had previously expected,” said archeologist Robert J. Braidwood of the University of Chicago. That age would make the chicken roughly contemporaneous with the pig as the first animals domesticated for food--about a thousand years earlier than sheep and goats and as much as 4,000 years before cattle. Dogs, however, were tamed for their companionship about 2,000 years earlier than chickens were first bred for food.
What makes the situation with chickens unique, said molecular biologist Susumu Ohno of City of Hope, is that the red junglefowl is still the cock of the walk, roaming wild in Southeast Asia. The precise predecessors of all other domesticated animals have long since gone extinct.
Humans almost certainly ate chickens long before domesticating them. But starting 10,000 years ago, villagers began raising and breeding chickens to provide a more stable food supply. Ohno conducted the research in collaboration with several colleagues in Japan, one of whom was Akishinonomiya Fumihito, second son of Japan’s emperor. The Japanese royal family has a long history of interest in biological research.
The team used well-established techniques to compare subtle differences in the DNA of mitochondria from a broad variety of chickens and wild fowl, including pheasants and quail. Mitochondria are small energy-producing packets within cells that contain their own DNA that is distinct from that of the cell itself. Because mitochondrial DNA mutates more rapidly than cellular DNA, changes in it provide a good yardstick for dating events that occur on a scale of thousands of years.
Those techniques showed that all the breeds of chickens they studied share a common ancestor and that the ancestor was genetically identical to the red junglefowl. There is no trace of genes from pheasants or quails in the current birds, they also found.
As recently as the 1960s, archeologists had believed that the chicken was domesticated only about 4,000 years ago, probably in the Indus Valley of Pakistan. That idea became outmoded when researchers discovered 7,500-year-old bones at 16 sites along the Yellow River in northeast China. Few believed that to be the site of domestication, however, because the semiarid steppes of the region did not harbor wild species from which the chicken could have descended.
The new findings fit in well with the previous chronology, according to Ohno, because both humans and junglefowl inhabited the target area at the right time. It is unlikely that archeologists will ever discover chicken bones from that period in the region because temperature and humidity conditions would make the bones disappear almost as fast as a box of Chicken McNuggets.
