Human Migrations #2: Australia

Yesterday, I wrote about a couple of papers on the possible Taiwanese origins of the Lapita culture. What struck me was the way these two separate studies—historical linguistics and DNA analysis—intermesh and then feed back into the archaeological data. The papers are evidence that researchers are using the archaeological notions to carry out a scientific study of the past in other disciplines and then recursively referring back to the archaeological data. I think that's interesting, don't you?

The other part of the genetic study of the human bacteria Helicobactor pylori led into the discussion of the original peopling of Australia.

Current archaeological theory about the populating of Australia argues that the population of the Sahul—an ancient land created by lowered sea levels and combining Australia, Tasmania and New Guinea—happened once. People left Africa about 60,000 years ago and likely followed the Southern Dispersal Route, reaching the Sahul between 40,000-50,000 years ago; that arrival date is based on a handful of admittedly somewhat controversial archaeological sites in Australia that date older than 40,000 years ago. But, using the genetic varieties of H. pylori, Moodley et al. shorten that timeline, dating the split from Asia to between 31,000 to 37,000 years ago (within a 95% confidence level). They, like archaeologists, argue that the populating only occurred once.

That leaves problematical the evidence for a handful of sites like Lake Mungo and Devil's Lair. It's possible that the people who made those ancient sites didn't survive to make up part of the modern population, or it's possible that one set of dates, archaeological or genetic, are off by a few thousand years. Dating by genetic mutation is always tricky—in some cases the dates are wildly off from archaeological evidence—there's actually quite a few possibilities.

Dates aside, the occurrence of H. pylori in modern populations today supports the basic theory developed for the track of human migration out of Africa, along the Southern Dispersal Route and into the Sahul. And that is pretty interesting.

Sources, etc.

Moodley, Yoshan, et al. 2009 The Peopling of the Pacific from a Bacterial Perspective. Science 323(23):527-530.

• Populating Australia
• Tracking Human Migrations
• Map of the Peopling of Austronesia