How the wild jungle fowl became the chicken | Science

From chicken biryani to khao mun gai, chicken and rice is a winning combo worldwide. But the two are more inextricably linked than even chefs realized. A pair of new archaeological studies suggest that without rice, chickens may have never existed.

The work reveals that chickens may have been domesticated thousands of years later than scientists thought, and only after humans began cultivating rice within range of the wild red jungle fowl, in Thailand or nearby in peninsular Southeast Asia, says Dale Serjeantson, an archaeologist at the University of Southampton who was not involved with the research. The studies, she says, have “dismantled many of the hoary myths about chicken origins.”

Charles Darwin proposed that chickens descended from the red jungle fowl—a colorful tropical bird in the pheasant family–because the two look so much alike. But proving him right has been difficult. Five varieties of jungle fowl range from India to northern China, and small chicken bones are rare in fossil sites.

In 2020, a study of 863 living chickens’ genomes confirmed that the jungle fowl Gallus gallus spaedicus subspecies was the ancestor of living chickens; chickens share more of their DNA with that subspecies than other types of jungle fowl. That in turn narrowed the site of domestication to Southeast Asia. Researchers have proposed fossils as early chickens dating back 8000 to 11,000 years ago in northern China and Pakistan. But genetics of living birds could not narrow the window for domestication, says geneticist Ming-Shan Wang, a postdoc at the University of California, Santa Cruz, first author of the genetic study. And they have not been able to get enough ancient DNA from fossil chickens to pinpoint the date. So paleo-anatomist Joris Peters of Ludwig Maximilian University of Munich teamed up with Greger Larson, a bioarchaeologist at the University of Oxford who is an expert on animal domestication. The duo organized an international team that began a comprehensive reevaluation of chicken bones, their dates, and records on them, from more than 600 archaeological sites around the world. In a separate study, the group directly dated chicken bones found in western Eurasia and Northern Africa.

They found the oldest bones of likely chickens came from a site called Ban Non Wat in central Thailand, where farmers grew rice 3250 to 3650 years ago, the team reports today in the Proceedings of the National Academy of Sciences. Farmers buried many skeletons of young members of the genus Gallus as grave goods along with other domesticated animals—strong evidence that these birds were domesticated chickens, rather than wild jungle fowl. The researchers propose that the rice seeds drew wild jungle fowl to rice fields, where the birds nested in thickets at the edge of the fields and got used to humans.

As the scientists traced the trail of chicken bones across Asia into the Middle East and Africa, they found a “striking” correlation between the spread of dry rice farming, millet, and other grains—and the appearance of chickens. Chickens appeared about 3000 years ago in northern China and India, the team found, and about 2800 years ago in the Middle East and Northeast Africa. The studies finding earlier chickens were flawed, the team argues, because either the fossils were not chickens or the dates were inaccurate.

To find out when chickens first entered Europe, members of the team directly re-dated bones from 23 of the proposed earliest chickens in Europe and Asia. The first chickens in Europe were found in an Etruscan site in Italy 2800 years ago, the team reports in Antiquity today.

The study is backed up by historical records, too—including the Bible. “Chickens don’t feature in the Old Testament,” says the study’s lead author Naomi Sykes, an archaeologist at the University of Exeter. “They burst onto the scene in the New Testament.”

Researcher compares leg bones of an ancient and modern chicken
When researchers re-dated these chicken bones from England and Bulgaria, they found that the supposedly ancient one from Bulgaria dated instead to the 20th century.Jonathan Rees/Cardiff University

It took another 1000 years before chickens spread north to Britain (with the Romans), Scandinavia, and Iceland. The subtropical birds likely had to adapt to the colder climates, says archaeologist Julia Best of Cardiff University, who was involved in both studies.

Still, it’s only recently that humans began to think of the birds primarily as food. Initially, people traded them as exotic possessions, valued for their feathers, coloring, and loud crow at first light, based on how they were depicted in art and buried as prized grave goods, Sykes says. Early chickens were smaller, she notes, and not a major source of meat. But the team’s review shows that about 500 years after chickens are introduced to each new place, they lose their special status and become an ordinary food.

The studies show that “the dispersal of domestic chickens is a more recent event than has been expected in the past,” says Masaki Eda, a zooarcheologist at Hokkaido University.

Still, Eda says he’d like to see follow-up research to make sure the bones in Thailand are definitely domesticated chickens, not wild junglefowl buried with humans. He also wants researchers to survey other sites in Southwest Asia to connect the dots showing where and how chickens were domesticated as rice and millet cultivation spread throughout Eurasia.

Even though chickens were domesticated later than other animals, they have become the most successful domesticated species on the planet, Larson says. Today, at 80 billion strong, they outnumber us 10 to 1. “This isn’t just about chickens or rice,” Sykes says. “How humans relate to chickens is a brilliant lens to understand how humans relate to the natural world.”

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