Their cheatin’ hearts, that’s how. From ScienceDaily:
New research led by Oxford University and Queen Mary University of London has resolved a pig paradox. Archaeological evidence has shown that pigs were domesticated in the Near East and as such, modern pigs should resemble Near Eastern wild boar. They do not. Instead, the genetic signatures of modern European domestic pigs resemble European wild boar…
The findings revealed that the first pigs to arrive into Europe alongside farmers 8,000 years ago had clear Near Eastern genetic ancestry. Over the course of the next 3,000 years, however, ancient domestic pigs hybridised with European wild boar to such an extent that they lost almost all their Near Eastern ancestry. Some low level of Near Eastern ancestry, however potentially remained in the genome of modern European domestic pigs, and this likely explains their characteristic black, and black and white spotted coat colours. Higher level of Near Eastern ancestry were also maintained in pig populations on Mediterranean islands maintained probably because these populations experienced comparatively less gene flow with European wild boar relative to pigs on the continent.
Professor Greger Larson, Director of the Palaeogenomics & Bio-Archaeology Research Network (PalaeoBarn) at Oxford and senior author of the study, said: “Having access to ancient genomes over such a large space and time has allowed us to see the slow-motion replacement of the entire genome of domestic pigs. This suggests that pig management in Europe over millennia was extensive, and that though swineherders maintained selection for some coat colours, domestic pigs interacted with wild boar frequently enough that they lost the ancestral signature of the wild boar from which they were derived.” Paper. (access?) – Laurent A. F. Franz et al., Ancient pigs reveal a near-complete genomic turnover following their introduction to Europe. Proceedings of the National Academy of Sciences, 2019; 201901169 DOI: 10.1073/pnas.1901169116 More.
Pigs ran wild and look what happened. Funny how a genome can be sort of a river like that. And they’re all still pigs.