A new understanding of how pigs were domesticated from wild boars is reported in a paper published online this week in Nature Genetics. The study found that one of the major assumptions used in animal domestication research is incompatible with genetic data from modern wild boars and domestic pigs.
Humans domesticated animals from wild species for agricultural purposes thousands of years ago. It is assumed that this process involved permanently isolating a relatively small number of individuals from the wild population.
Laurent Frantz and colleagues studied genetic data from more than 600 domestic pigs and wild boars in Europe and Asia. These data indicate that domestic pigs in Europe originated from Asian domestic pigs, as expected, but that they also share a large portion of their DNA with European wild boars. The authors tested several evolutionary models and found that the data were best explained by domestic pigs having interbred with wild boars throughout their history. Thus, domestic pigs are a mosaic of many wild populations, including possibly extinct ones, at least for European breeds. The data from Asian pigs suggested a similar mode of domestication but were not conclusive. The authors speculate that continuous selection by humans for agriculturally important traits counteracted the effect of this interbreeding, allowing domestication to continue.