Which came first: the domesticated chicken or its egg?

The chicken or the egg paradox is flummoxing enough, but apparently the domestication of chickens has been almost as baffling to science. Until now.

New international research provides evidence for where, when, and how humans domesticated chickens. The results show the way in which chickens were perceived in human society over the past 3500 years.

Cracking the mystery of chicken domestication has also shattered earlier beliefs about this history.

Previously, researchers have claimed that chickens were domesticated up to 10,000 years ago in China, southeast Asia or India, and that they appeared in Europe more than 7000 years ago.

Publishing their results in the Antiquity journal and The Proceedings of the National Academy of Sciences USA (PNAS), experts have shown this to be false. Their research shows that the arrival of dry rice farming in southeast Asia likely led to the domestication of the chicken’s wild ancestor, the red jungle fowl (Gallus gallus).

 “The fact that chickens are so ubiquitous and popular today, and yet were domesticated relatively recently is startling,” says Dr Ophélie Lebrasseur, from France’s Paul Sabatier University.

“Our research highlights the importance of robust osteological comparisons, secure stratigraphic dating and placing early finds within their broader cultural and environmental context.”

Acting as a magnet for roosting fowl, dry rice catalysed the closer relationship between the chicken’s ancestors and people.

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The international researchers found that this process was under way by about 1500 BC. Chickens would then have been transported across Asia before being moved throughout the Mediterranean by early Greek, Etruscan and Phoenician maritime traders.

“With their overall highly adaptable but essentially cereal-based diet, sea routes played a particularly important role in the spread of chickens to Asia, Oceania, Africa and Europe,” says lead author of the PNAS paper Professor Joris Peters, from the Ludwig Maximilian University of Munich in Germany.

Chickens weren’t always considered food, the researchers say. Several of the earliest chickens were buried alone and un-butchered. Many were even found buried with people. It was during the Roman Empire that chickens and their eggs were popularised as food.

The one on the left comes from Weston Down in England, and dates to 387–204 cal BC (in the Middle Iron Age); this hen was buried in a pit whole. Credit: Cardiff University.

“Eating chickens is so common that people think we have never not eaten them. Our evidence shows that our past relationship with chickens was far more complex, and that for centuries chickens were celebrated and venerated,” explains Professor Naomi Sykes from the University of Exeter in the UK.

Looking at chicken remains from more than 600 sites in 89 countries, the team examined bones, burial locations and historical records. The oldest bones attributable with certainty to a domestic chicken come from Ban Non Wat in central Thailand, and are between 3650 and 3250 years old.

Julia Best comparing a leg bone (the tibiotarsus) from an ancient and a modern chicken. The large specimen on the right comes from Hotnitsa in Bulgaria, and radiocarbon dating revealed that it was modern (20th century), rather than Neolithic/Bronze Age as previously proposed. The image also demonstrates the shape and size difference often visible between ancient specimens and large modern meat birds. Credit: Cardiff University.

Radiocarbon dating also helped establish age of 23 of the earliest-known chickens in western Europe and northwest Africa. The results show that domesticated chickens arrived in Europe only about 2800 years ago and took another 1000 years to reach the colder climates in the continent’s north.

“This is the first time that radiocarbon dating has been used on this scale to determine the significance of chickens in early societies,” says lead author of the Antiquity paper Dr Julia Best, from the UK’s Cardiff University.

“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.”

Julia Best, from Cardiff University, discusses the research on chicken domestication.

Professor Greger Larson, of the University of Oxford, also in the UK., adds: “This comprehensive re-evaluation of chickens firstly demonstrates how wrong our understanding of the time and place of chicken domestication was.

“And even more excitingly, we show how the arrival of dry rice agriculture acted as a catalyst for both the chicken domestication process and its global dispersal.”

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