Humans preferred their pigs to be black

Black feral pigs in China, Europe and Polynesia all have different genetic mutations which have led to their black colour. This suggests that in the course of history, the pigs have been selected for their black coat more than once by humans keeping the animals.

This was concluded by researchers from the United Kingdom, United States, Canada, Sweden, Spain and Ireland. The study was recently published in Royal Society Open Science.

Origins of Hawaiian feral pigs

The researchers dived into the origins of Hawaiian feral pigs, in order to get a better understanding of the native plant and animal population on the island.

The researchers indicate in their study that, although pigs were brought to Hawaii for the first time by Polynesian explorers around 800 years ago, it was long suggested that the current pig population in Hawaii descends primarily or even exclusively from European pigs. These would have first been brought to the islands in 1778 when Captain Cook explored Polynesia.

Investigating markers on a genetic level

The team led by professor Greger Larson, University of Oxford, analysed a neutral mitochondrial marker and a functional nuclear coat colour marker in 57 feral Hawaiian pigs.

Through the identification of a new mutation in the MC1R gene that results in black colouration, they demonstrated that Hawaiian feral pigs are mostly the descendants of those originally introduced during Polynesian settlement, though there is evidence for some admixture.

No wild boars have black colours

Prof Larson, attached to the Palaeogenomics and Bio-Archaeology Research Network at the University of Oxford, told the website Phys.org: “The first pigs introduced to Hawaii by the Polynesians were kept as domestic animals. No wild boar has black colours since natural selection only allows camouflaged pigs to survive long enough to reproduce.

“Humans, on the other hand, love all kinds of coloured coats and have chosen for black coats at least 3 times independently in domestic pigs in Europe, Asia, and the Pacific. In the case of pigs, black has always been the new black.”

Not exclusively descended from European feral pigs

As such, extant Hawaiian pigs represent a unique historical lineage that is not exclusively descended from feral pigs of European origin.

The research was done by Greger Larson, Vincent Battista, Laurent Frantz and Ross Barnett, University of Oxford, UK; Anna Linderholm, Texas A&M University, College Station, TX, United States; Daisy Spencer, National University of Ireland, Galway, Ireland; Robert C. Fleischer, National Zoological Park, Washington, DC, United States; Helen F. James, Smithsonian Institution, Washington, DC, United States; Dave Duffy, University of Hawaii at Manoa, HI, United States; Jed P. Sparks, Cornell University, Ithaca, NY, United States; David R. Clements, Trinity Western University, Langley, BC, Canada; Leif Andersson, Uppsala University, Uppsala, Sweden; Keith Dobney, University of Liverpool, Liverpool, UK; Jennifer A. Leonard, Estación de Biológica de Doñana, Seville, Spain.