

By tracking the evolution of language and gut bacteria, scientists may have settled a debate over the spread of humans across the Pacific.

The evolutionary trajectory implied by words and bugs begins with an initial migration from Taiwan 5,000 years ago, with a first wave of people spreading to the Philippines and a second to western Polynesia.

The findings, writes University of Cambridge archaeologist Colin Renfrew, "mark a substantial advance in our understanding of human population history" — and they involve some cutting-edge archaeological sleuthing to boot.

Physical remains, rather than linguistic patterns and microbes, are the preferred form of evidence for human migratory maps. Population genetics has also proved useful, with the progressive differences between modern and ancient DNA samples forming a biological tapestry of human history. But archaeologists attempting to understand the settlement of far-flung Pacific islands have been stymied by a lack of hard evidence, and genetic studies have proven inconclusive.

As a result, some historians concluded that settlement occurred gradually, over the last 30,000 years, by descendants of an initial population from inland southeast Asia — the so-called "slow boat from Wallacea" theory. Others hypothesized a recent, Taiwan-based origin.

In the latest analyses, published Thursday in Science, researchers abandoned traditional tools in favor of languages and Heliobacter pylori, a microbe that has co-evolved with humans for at least 50,000 years.

Bacterial samples taken from modern aborigines in Taiwan, Australia, Melanesia, Polynesia and New Guinea reveal a common, 5,000-year-old Taiwanese ancestor, which varied as human populations took their stomach bugs to the Philippines 3,000 years ago and then, several hundred years after that, to Western Polynesia and New Zealand.

A separate analysis of of 210 core vocabulary words in 400 Pacific-region languages produced an evolutionary tree of culture rather than organisms — and its branches followed with the migratory routes suggested by H. pylori's locale-specific evolution.

"The use of modern genetic data to reconstruct phylogenetic trees shows that the past is still 'within us' today," wrote Renfrew in a review of the studies. "Our past is within us in a different sense when the vocabularies of specific modern languages are the basis for historical analysis. And the past is within us in a very literal way when the early history of humankind is reconstructed based on the bacterial flora in our guts."

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Citations: "Language Phylogenies Reveal Expansion Pulses and Pauses in Pacific Settlement." By R. D. Gray, J. Drummond and S. J. Greenhill. Science, Vol. 323 Iss. 5913, Jan. 22, 2009.*

"The Peopling of the Pacific from a Bacterial Perspective." By Yoshan Moodley, Bodo Linz, Yoshio Yamaoka, Helen M. Windsor, Sebastien Breurec, Jeng-Yih Wu, Ayas Maady, Steffie Bernhöft, Jean-Michel Thiberge, Suparat Phuanukoonnon, Gangolf Jobb, Peter Siba, David Y. Graham, Barry J. Marshall, Mark Achtman. Science, Vol. 323 Iss. 5913, Jan. 22, 2009.

"Where Bacteria and Languages Concur." By Colin Renfrew. Science, Vol. 323 Iss. 5913, Jan. 22, 2009.

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Images: 1. Flickr/SF Brit. 2. AAAS/Science. On top: Distribution of H. pylori populations in Asia and the Pacific, color-coded by type. Below: The different Austronesian languages, correlated with the H. pylori status of their speakers.*

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