Pacific Pigs: How They Island-Hopped with Humans

For tens of thousands of years, humans have transported pigs across islands, shaping the genetic makeup of populations from Southeast Asia to Polynesia, according to a new study. The research reveals multiple waves of human-assisted pig dispersal, resulting in a complex genetic “melting pot” and challenging traditional definitions of “invasive” species.

Pigs Ferried Across Islands

An international team of experts analyzed whole genomes from over 700 pigs to trace this history, reconstructing when different pig lineages arrived on specific islands, how they mixed with local species, and which human migrations likely carried them. The result is a sweeping timeline of human-assisted dispersal – multiple waves, many origins, and a lot of interbreeding.

Ice Age Pig Pioneers

The earliest evidence suggests people moved pigs as far back as 50,000 years ago on the island of Sulawesi, known for its ancient cave art. Those artists not only painted Sulawesi’s warty pigs, but also transported them south and east, likely to establish future hunting stock.

Pigs Moved With Farmers

Around 4,000 years ago, early agricultural communities began transporting domestic pigs across islands in Southeast Asia, starting in Taiwan and spreading through the Philippines, Maluku Islands, Papua New Guinea, Vanuatu, and Polynesia. Domestic pigs often escaped and hybridized with wild or earlier introduced relatives.

On the Komodo Islands, for example, today’s pigs carry ancestry from both domestic swine and ancient Sulawesi warty pigs, forming a hybrid population that serves as prey for endangered Komodo dragons.

Colonial Pigs Enter Islands

The study also identified genomic fingerprints of European pigs introduced during the colonial period, adding another layer of ancestry to island herds.

“When people have lent a hand, pigs were all too willing to spread out on newly colonized islands in Southeast Asia and into the Pacific,” said Greger Larson, a professor at the University of Oxford.

Rethinking Invasive Species

The research underscores the profound and long-lasting impact humans have had on Pacific ecosystems. In some places, pigs are culturally significant, while in others, they are considered pests. On certain islands, they’ve been present for so long that locals view them as native fauna.

Policy will need to reflect this complexity. Control or removal may be essential on water-stressed islands, while eradication could be harmful in places where pigs now support predator diets or local livelihoods.

“The big question now is, at what point do we consider something native? What if people introduced species tens of thousands of years ago, are these worth conservation efforts?” said Laurent Frantz, a professor of animal paleogenomics at Queen Mary University of London.

A Melting Pot of Ancestries

Disentangling this history required dense sampling across islands and time periods, plus careful modeling to identify lineage splits, mingling, and gene flow. “These movements led to pigs with a melting pot of ancestries,” said Professor David Stanton, a geneticist from Cardiff University.

People Carry More Than Culture

The study highlights that human migration is a biological force, with seafarers carrying not only cultural artifacts but also genomes. Some introduced species, like pigs, have reshaped entire island ecosystems.

Protecting native biotas remains vital, but some introduced lineages have become so intertwined with local ecologies that a strict “remove the nonnative” approach may no longer be appropriate. Good conservation in the Pacific will likely require place-by-place decisions informed by genetics, ecology, and community needs.

The full study is published in the journal Science.