Since our species first appeared, our ancestors have mostly lived in small groups; networks of nomadic or settled communities that were often widely dispersed across the landscape, in striking contrast to the large, urbanized and highly inter-connected societies that have emerged within the last few thousand years. Small traditional societies that resemble prehistoric settings have been lost in most regions, including large parts of Europe, Africa, Asia and the Americas, by frequent post-Neolithic population movements. Further population restructuring has been driven by the actions of modern states during the historic era (for instance, see Leslie, et al. 2015 for a history of these processes in the British Isles). As a result, where small, seemingly traditional communities exist, their histories may extend only into the recent past.
An intriguing exception is Iceland, where parish records include the births, marriages and deaths of the entire population from the time the island was first colonized in the 9th century. These records have enabled geneticists to track the transmission of genes related to health over the centuries. Knowing each person’s complete genealogy on both the father’s and mother’s side, it becomes possible to follow specific genes from one generation to the next. In this way, geneticists discovered more than 8000 individuals with so-called 'knockouts' – rare genetic mutations that disable genes – and traced the consequences of these knockouts in the evolving population. A similar study in neighboring Scandinavia would be impossible, because there have been many population movements, and genealogies would be partial at best. But despite its advantages, the Icelandic study is limited in scope, because the population is small (325,000) and homogeneous, with relatively little genetic variation.
The islands of the more remote regions of Island Southeast Asia and Oceania offer the chance to undertake more ambitious studies. The history of Iceland as an isolated population goes back a thousand years. In contrast, the Austronesian islands were colonized much earlier, there are a lot more of them, and their environments are more varied. But the most interesting difference concerns their origins. Iceland was colonized just once, but two great migrations reached the Oceanic islands. One, about fifty thousand years ago, took modern humans all the way from the Asian mainland to Australia. The second, which reached the islands about four thousand years ago, spread across half the globe and ended in the last great human expansion into pristine environments, the colonization of Oceania. By now, one might expect later population movements to have erased the traces of these migrations. Instead, as we will see in this chapter, like Iceland many Austronesian populations remained quite isolated after their initial colonization. Consequently, using genetic information it is possible to reconstruct detailed histories of both migrations, including what happened on the islands where the new arrivals met the descendants of the original Pleistocene migrations. These dated chronologies of population movements and mingling can be interpreted with insights from anthropology and linguistics. They offer perhaps the most comprehensive record of the evolution of social structure and language in what paleontologists call 'Deep Time'.
The first part of this chapter sets the stage with an account of the history of migrations into the islands, beginning with the earliest journeys out of Africa. The second part describes how we sought to make sense of the two biggest surprises in the genetic and linguistic data, and the third part explains the analytical models we developed. The time scale for the models runs from tens to hundreds of generations, and the spatial scale is Island Southeast Asia.
An intriguing exception is Iceland, where parish records include the births, marriages and deaths of the entire population from the time the island was first colonized in the 9th century. These records have enabled geneticists to track the transmission of genes related to health over the centuries. Knowing each person’s complete genealogy on both the father’s and mother’s side, it becomes possible to follow specific genes from one generation to the next. In this way, geneticists discovered more than 8000 individuals with so-called 'knockouts' – rare genetic mutations that disable genes – and traced the consequences of these knockouts in the evolving population. A similar study in neighboring Scandinavia would be impossible, because there have been many population movements, and genealogies would be partial at best. But despite its advantages, the Icelandic study is limited in scope, because the population is small (325,000) and homogeneous, with relatively little genetic variation.
The islands of the more remote regions of Island Southeast Asia and Oceania offer the chance to undertake more ambitious studies. The history of Iceland as an isolated population goes back a thousand years. In contrast, the Austronesian islands were colonized much earlier, there are a lot more of them, and their environments are more varied. But the most interesting difference concerns their origins. Iceland was colonized just once, but two great migrations reached the Oceanic islands. One, about fifty thousand years ago, took modern humans all the way from the Asian mainland to Australia. The second, which reached the islands about four thousand years ago, spread across half the globe and ended in the last great human expansion into pristine environments, the colonization of Oceania. By now, one might expect later population movements to have erased the traces of these migrations. Instead, as we will see in this chapter, like Iceland many Austronesian populations remained quite isolated after their initial colonization. Consequently, using genetic information it is possible to reconstruct detailed histories of both migrations, including what happened on the islands where the new arrivals met the descendants of the original Pleistocene migrations. These dated chronologies of population movements and mingling can be interpreted with insights from anthropology and linguistics. They offer perhaps the most comprehensive record of the evolution of social structure and language in what paleontologists call 'Deep Time'.
The first part of this chapter sets the stage with an account of the history of migrations into the islands, beginning with the earliest journeys out of Africa. The second part describes how we sought to make sense of the two biggest surprises in the genetic and linguistic data, and the third part explains the analytical models we developed. The time scale for the models runs from tens to hundreds of generations, and the spatial scale is Island Southeast Asia.
References:
Leslie S, Winney B., Hellenthal G et al. 2015. The fine-scale genetic structure of the British population. Nature 519:309-14.
Leslie S, Winney B., Hellenthal G et al. 2015. The fine-scale genetic structure of the British population. Nature 519:309-14.