About 3,500 years ago, pigs began making the harrowing journey to the most remote islands of the Pacific alongside their ancient human owners, and that partnership is revealing how the region was colonized.
The popular historical thinking has been that the entire pioneering group of proto-Malayo-Polynesians — humans, pigs and all of their additional living and cultural accoutrements — embarked from Formosa (present-day Taiwan) as a single unit.
A new DNA study of ancient and modern pigs suggests the geography might not be so simple.
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"The traditional thought is that people left Taiwan, went to the Philippines, then [dispersed] from there," said Greger Larson, a geneticist who led the study while at the University of Oxford in England. "They may have, but not with pigs."
Most of the languages of the Philippines, Malaysia, Madagascar, Indonesia and Polynesia are closely related. More distantly related languages are found only among Formosan aborigines, suggesting that the ancestors of Malays, Filipinos and Polynesians originated in Taiwan.
In the most recent edition of the journal Proceedings of the National Academy of Sciences, scientists from Oxford and Durham University in northern England propose that the pigs that ended up domesticated across the outermost Pacific Islands, such as French Polynesia and Hawaii, probably came instead from present-day Vietnam.
Pigs a constant companion
The findings challenge the established notions of just who reached outer Oceania first, and which route they took to get there.
Most historians agree that a first wave of humans left the Asian mainland around 50,000 years ago to settle New Guinea, Australia and a few island chains nearby. Their descendants include New Guinean highlanders and Australian aborigines.
A much later group left Formosa around 3,500 years ago and made direct, swift work of the untouched chains east of the Solomon Islands, it was thought.
That group is thought to have created the Lapita pottery-making culture of the Bismarck Archipelago and other Melanesian islands of the western Pacific, which flourished in the first millennium B.C. and was almost certainly ancestral to Polynesian culture.
"Pigs are part of the whole package very closely associated with the Lapita culture," Larson told LiveScience.
Excepting the rare absence of pigs on Easter Island, he said, "they're always associated with the first appearance of people in the Pacific. If you understand where the pigs are coming from, you know where people are coming from."
Pigs can't swim, he noted, so they literally followed humans everywhere they went.
Vietnamese boar made the jump
The researchers studied mitochondrial DNA drawn from ancient pig teeth fround at Lapita sites and now stored at museums, as well as from hair from modern feral pigs currently living in various places in the Pacific.
Unique characteristics of swine biology made it easy to tell how each pig was related, Larson said.
"For some reason, with pigs, there is a very strong correlation between their genetic signal and geographic signal. You can tell exactly where a pig is from based on this genetic marker," he said.
Comparing the DNA results with an existing catalogue of pig gene family trees, Larson and his team were able to figure out the Pacific pigs' closest Asian relations.
"The tree does a good job of showing dispersal routes across Asia. That is the natural pattern of wild boar migration — nothing to do with humans," he said. "Two pig specimens from Vietnam were the only ones that had the signature of the Pacific pigs. The boar found in Taiwan is completely different."
Challenges linear thinking
The study results should get anthropologists and historians thinking in broader terms when it comes to things like the trans-Pacific migration, Larson said.
"People tend to think of colonization and culture as moving in a single unit," he said, "but with history we've learned that the simplest answer is rarely the right one."
Another recent study, which found Lapita burials that mixed headless bodies and skulls of individuals from different Pacific islands, supports Larson's argument.
The Lapita people, "might have just come together in New Guinea from different parts of Asia, with separate groups bringing different parts of the culture with them," he said, and moving on to more outer lying islands from there.
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