Pigs imported from the Near East prompted European farmers to begin domesticating their own swine 11,000 years ago, according to a new genetic analysis. The finding sheds light on how animal husbandry spread throughout the ancient world.
Livestock herding originated in the Near East about 11,000 years ago, when sheep were first domesticated. Archaeologists have proposed three models for how animal husbandry later spread to Europe: Early farmers might have physically migrated to the west, the idea of herding might have spread through cultural diffusion, or Europeans may have tamed wild animals on their own.
To get a better picture, an international team led by archaeologists Greger Larson and Keith Dobney at Durham University in the U.K. extracted 221 samples of mitochondrial DNA from the jaws and teeth of wild and domesticated pigs. The specimens came from more than 140 archaeological sites in Europe and western Asia spanning 13,000 years. These ancient DNA sequences were compared to those from 323 modern pigs.
The team found that the first domesticated pigs in Europe, which showed up about 7500 years ago, had genetic markers of Near Eastern animals. This means that they were brought to the continent, probably by farmers who migrated west. Not long after pigs showed up, Europeans began to domesticate their own wild boars, which quickly replaced the Near Eastern imports. In just 500 years, the proportion of local genetic markers in Europe's domesticated pigs rose from 5% to 95%, the authors report online this week in the Proceedings of the National Academy of Sciences. The researchers suggest that the arrival of tame Near Eastern pigs might have inspired Europeans to domesticate their own animals.
So it appears that all three models of livestock domestication hold true, at least for the origins of pig husbandry in Europe. The same process may have occurred with domesticated cattle, whose wild ancestors also lived in both Europe and the Near East.
"This is a great paper and a very important contribution to the debate," says archaeologist Marek Zvelebil of the University of Sheffield, U.K. However, he notes that the authors have not completely ruled out the possibility that some Europeans were taming pigs before the arrival of the Near Easterners, which "would not be easily detectable through DNA analyses."
Simon Davis, a zooarchaeologist at the Portuguese Institute of Archaeology in Lisbon, further cautions that the study's validity depends on whether archaeologists correctly distinguished wild pigs from domestic pigs, which are smaller. Because these differences start out slight when domestication first begins, Davis says the team might be on "shaky ground" drawing conclusions about the earliest stages of domestication.