Pigs Aren’t Quite as Domesticated as People Once Thought

Researchers partially unravel the complexity of domesticated swine genetics

Domesticated pigs
Scott Bauer, U.S. Department of Agriculture - Public Domain via Wikimedia Commons

The world’s food system is largely built on the domestication of a few animals and a handful of plants. Figuring out when some human or group of humans first took wild stock or vegetation and started breeding for specific traits is a major undertaking for researchers looking to mark human milestones. Now, they’ve come closer to figuring out how that story played out for pigs. 

Modern domesticated pigs are a bit more wild than previously thought, reports Arielle Duhaime-Ross for The Verge. The wild boar still lurking in the genomes of European domesticated pigs arises from mixing of a handful of wild populations over time.

Typically, domestication is thought of a process that starts when humans isolate animals (or plants) from their wild version and keep them isolated while they breed for specific traits. However the real events rarely play out that cleanly. 

Even before the new study, the history of pigs’ metamorphosis from wild to domesticated seemed a little complicated and murky, reports Elizabeth Pennisi for Science. Pigs were domesticated twice — once in the Mekong valley of China and another time in Anatolia, a region in modern-day Turkey — both around 9,000 years ago. A 2007 study revealed that first pigs in Europe were brought there by farmers from the Near East, around 7,500 years ago, even though pigs may have also been domesticated from wild populations in western Eurasia around that time. Then European-based wild boar genetics soon largely supplanted the Near Eastern ones.

In this new paper, researchers delved into the details of more than 100 genome sequences from European pigs and used evolutionary models to explain the genetic mosaic they found. The picture was most consistent with interbreeding with wild populations long after the first period of domestication. They published their work in Nature Genetics

The findings lend credence to the interpretation that wild boar in Europe were never domesticated independently, but rather the presence of their genes in European pigs comes from interbreeding. Some of the genes in modern pigs appear to have come from populations of wild boar that are now extinct.

However, the researchers still aren’t sure if this mix was intentional, or the result of accidental encounters between kept pigs and wild ones, Duhaime-Ross writes for The Verge. "Going back in time would be the best thing to do," says study co-author, Martian Groenen, who is a geneticist at Wageningen University in the Netherlands. "The fossil record might be able to answer some of these questions."

A similar type of confusion still plagues the timeline of domestication in dogs. But that doesn’t prevent people from enjoying the fruits of thousands of years of labor: companionship in the case of dogs and bacon and more in the case of pigs. Well, sometimes people enjoy companionship in pigs as well — though perhaps some don’t realize that owning a pet pig isn’t always practical.

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