Two new studies by an international team of researchers—one published June 6 in PNAS and the other June 7 in Antiquity—attempt to clarify the relationships chickens had with ancient human civilizations. Rather than a longstanding domestication, researchers now think that the tree-dwelling ancestors of modern chickens, the red junglefowl (Gallus gallus spaedicus), first entered human settlements to capitalize on early rice cultivation in southeast Asia, and that they only did so roughly 3,500 years ago—much earlier than previously thought. But rather than becoming a source of food, these early birds became cultural icons, only finding their way to the dinner plate much later.
“Eating chickens is so common that people think we have never not eaten them,” Naomi Sykes, an anthropologist at the University of Exeter who was involved in both studies, tells The Guardian. “Our evidence shows that our past relationship with chickens was far more complex, and that for centuries chickens were celebrated and venerated.”
The current work adds to a longstanding debate over just how long chickens have been domesticated. Bones found at sites in China and Pakistan suggest that chickens may been residents of human settlements as long as 8,000 to 11,000 years ago, but several factors complicate the narrative: their bones can easily be confused for other species of fowl, New Scientist reports, and bones can get moved around into older layers of sediment, making them seem older. This latter possibility was borne out in the Antiquity study, when radiocarbon dating revealed that one bone suspected of being 7,500 years old actually belonged to a chicken that lived as recently as the 1980s.
Indeed, the radiocarbon dating of 23 bones from western Eurasia and northern Africa by the team revealed that 18 were younger than previously thought, sometimes by thousands of years. “This is the first time that radiocarbon dating has been used on this scale to determine the significance of chickens in early societies,” Cardiff University bioarchaeologist Julia Best, who worked on both studies, tells The Guardian. “Our results demonstrate the need to directly date proposed early specimens, as this allows us the clearest picture yet of our early interactions with chickens.” Speaking to New Scientist, Best adds that the findings weren’t entirely surprising, noting that “we had begun to have an inkling that some of the earliest bones were probably not as ancient as had been claimed.”
To better pinpoint just when and where chickens first began engaging with humans, the PNAS study analyzed bones from 600 sites in 89 countries and applied various tools—including morphological and osteometric assessments along with written or otherwise documented evidence of chickens in the region—to infer the relationships between the birds and humans. That’s what led to the hypothesis that chickens likely first became domesticated in response to rice cultivation, which “created a more open, less [tree-covered] environment, which is actually an environment where red junglefowl thrive,” Ophélie Lebrasseur, a zooarchaeologist at the Centre for Anthropobiology and Genomics of Toulouse in France who worked on both studies, tells New Scientist.
The earliest definitive evidence of domestication came from a dry, rice-farming site in Thailand called Ban Non Wat that dates to between 1650 BCE and 1250 BCE, Science News reports. As cultivation of rice, and later millet, increased, it likely drew birds out of the trees and into the settlement more permanently. Chickens were found buried alongside humans in graves, strongly suggesting they were domesticated, Science reports. The chickens later spread across Asia in a way that seems to be correlated with the expansion of grain farming, and then throughout the Mediterranean along routes used by Greek, Etruscan, and Phoenician traders, according to The Guardian. Roman soldiers helped expand the range of poultry still further, bringing them to England roughly 1,700 years ago.
University of Sydney archaeologist Keith Dobney, who did not participate in either study, tells Science News that the PNAS study combines a trove of new data “into a fully coherent and plausible explanation of not only where and when, but also how” chickens were domesticated.
Dale Serjeantson, an archaeologist at the University of Southampton who was not involved with the research, tells Science that the two studies together have “dismantled many of the hoary myths about chicken origins.”
Researchers in the current work note that they aren’t entirely sure why people took the next step with chickens, from simply allowing them near settlements to the kind of breeding and raising that made them domesticated. They failed to find evidence that the chickens were being slaughtered for consumption in those early days, although New Scientist reports that they could have been used for their eggs.
Other hypotheses suggest that perhaps the birds functioned as security alarms, warning people of intruders, according to New Scientist. Another, based on findings that chickens were sometimes buried alongside humans, is that they may have served as spiritual guides to usher people into the afterlife. “There were some associations with deities,” Best tells New Scientist.
Regardless, once the chickens arrived in each new place, it seems to have taken only a few centuries for them to become a common source of protein. Today, chickens are the world’s most numerous domestic animal, the PNAS study reports, all because those first curious birds struck up a relationship with rice farmers. However, “this isn’t just about chickens or rice,” Sykes tells Science. “How humans relate to chickens is a brilliant lens to understand how humans relate to the natural world.”