This article says that recent work with DNA seems to say that Europe was colonized from the middle east, and that middle-eastern pigs were brought in as part of that migration. But when the local pigs got domesticated, within 500 years the original middle eastern pigs had been completely replaced by the European hogs, and that the European hogs even managed to go back into the middle east and completely replace the original hogs.
Something similar has happened with the American food chain. The Duroc breed of pig is the most efficient at turning feed into lean pork, and for the most part has completely replaced every other breed of pig in commercial pig farms, in the same way that Cornish cross chickens have replaced the majority of other breeds in commercial meat chicken farms.
It turns out that pigs weren't the only things that got replaced. Early European settlers got replaced by later Immigrants, too.