Evolution of the Barnyard Chicken: Ancient Bone DNA Reveals Rapid Changes

It turns out that the chickens of today are a lot different from the chicken that lives a few hundred years ago. Scientists have taken a look at the DNA from the bones of birds that lived 200 to 2,300 years ago in Europe, and have found that they've evolved drastically since then.

Scientists previously believed that any mutations that are widespread in domestic plants and animals but are absent from their wild cousins actually played a key role in the domestication process. These mutation spread as people and their livestock moved across the globe. Yet a growing number of ancient DNA studies actually tell a different tale.

Chickens are actually descended from a wild bird called the Red Junglefowl. Humans started raising this bird between 4,000 and 5,000 years ago in South Asia. In order to better understand the evolution of this bird, the researchers examined DNA from the skeletal remains of 81 chickens taken from a dozen archaeological sites across Europe.

So what did they find? They discovered that a gene associated with yellow skin color, called BCDO2, was actually introduced far later than previously expected. In fact, it probably only became prevalent in domesticated chickens as late as 500 years ago. The same can be said for a gene involved in theroid hormone production, called TSHR, which is implicated in a chicken's ability to lay eggs year-round.

"It's a blink of an eye from an evolutionary perspective," said Greger Larson, one of the researchers, in a news release. He went on to say, "Just because a plant or animal trait is common today doesn't mean that it was bred into them from the beginning. It demonstrates that the pets and livestock we know today-dogs, chickens, horses, cows-are probably radically different from the ones our great-great-grandparents knew."

The findings are published in the journal Proceedings of the National Academy of Sciences.