Pigs were domesticated independently at least seven times around the globe, a new study has found.
All domestic pigs in Europe are descended from European wild boar
The discovery was made by linking the DNA of tame porkers with their wild relatives, Science magazine reports.
Researchers found farmed pigs in several locations were closely related to wild boar in the same region, suggesting local domestication.
This challenges the notion that boar were tamed just twice before being transported throughout the world.
"Many archaeologists have assumed the pig was domesticated in no more than two areas of the world, the Near East and the Far East, but our findings turn this theory on its head," said Keith Dobney, of the University of Durham, UK.
"Our study shows that domestication also occurred independently in Central Europe, Italy, Northern India, South East Asia and maybe even Island South East Asia."
Trade and migration
Archaeological evidence suggests the pig was first domesticated 9,000 years ago in Eastern Turkey. They were also domesticated in China at around the same time.
Until now, archaeologists generally assumed that after their initial domestication in these two locations, tame pigs were transported - through trade and human migration - around the world.
In many ways, this is the simplest explanation: as farming methods spread during the Neolithic Age, new innovations and domestic animals were thought to have been passed through the human population.
But it seems the truth is a little more far fetched. Instead of importing tame pigs, people from several different countries domesticated the animals themselves.
"There is definitely something a bit weird about it," said co-author Greger Larson, of Oxford University, UK. "Maybe people really didn't bring pigs with them during the agricultural sweep as part of the Neolithic.
"Maybe instead of bringing pigs with them they were domesticating wild boar only."
Transfer of ideas
However, because the researchers have not been able to date the recently discovered centres of domestication, it is unclear whether the idea of taming pigs was had independently, or whether it was transferred between communities.
The team found that all domestic pigs in Europe are descended from European wild boar - and not Near Eastern boar - which means farmers travelling west from Turkey were not bringing significant numbers of pigs with them.
But that does not mean they did not bring the good idea of pig domestication with them.
Nonetheless, it raises questions about the process of animal domestication, and the spread of agricultural ideas.
"Domestication probably isn't just one guy having an ingenious idea and looking at a wild boar and saying, 'I can get a domestic pig out of that'," Dr Larson said. "It could be that domestication is almost a natural consequence of people settling down to farm.
"These findings are forcing the question about the origins of domestication across all animals."