European pig producers have found a lucrative market selling porkers to China for breeding purposes.
But a study published on Tuesday shows that this business is a remarkable tale of trade flowing in reverse.
The super-pigs exported to China these days are distant descendants of Chinese pigs that were brought into Europe around two centuries ago to improve cantankerous local hogs.
Domesticated pigs trace their lineage back to wild boars -- Latin name Sus scrofa -- that originated in Southeast Asia around four million years ago, according to the study.
The species expanded its geographical range over the aeons, eventually developing into two very distinct populations -- the farmed pig of East Asia and the European wild boar.
Writing in the journal Nature Communications, a team of geneticists led by Mirte Bosse of Wageningen University in the Netherlands sequenced the DNA of 70 pig breeds from across Europe and Asia.
They found telltale signatures, or haplotypes, from Chinese breeds that were brought into European boars in the late 18th and early 19th century -- a trade that is also spelt out in commercial documents of the time.
Chinese pigs brought in "great mothering characteristics, superior meat quality, strong resistance to diseases, better adaptation to living in sties and producing large litters" of 15 piglets or more, the paper said.
"Our findings provide a unique insight into the genomic haplotype patterns resulting from breeding practices from first domestication until the intensive breeding industry we know today."