Wednesday, October 17, 2012

Madagascar's Peopling




We have posted on this in the past but the key take home here is that a ship load or perhaps even an expedition similar to Polynesian expeditions took off from Indonesia and went with the winds until they fetched up on Madagascar. What is noteworthy is just how small a founding group can be. It is thus easy to backtrack for the far greater occupations of continents that also likely were smallish one way trips.

The real problem is just how recent that event was. Sea beds have been much lower and many more islands could have acted as stepping stones. I find it difficult to believe that a prior population did not exist and live there. It may even have been wiped out or simply have not succumbed to intermarriage until much later when Africans had arrived and larger settled populations drew down against subsistence hunters.

It will take careful archeology to show any of this and I suspect no one is looking too hard yet.


A.D. 830: A storm sends an Indonesian trading ship drastically off course. Months later, dozens of ragged survivors make landfall on an island off the southeast coast of Africa, more than 3,000 miles from home. Today,Murray Cox, a computational biologist at New Zealand’s Massey University, says a scenario like this may describe the murky origins of the first permanent settlements on Madagascar, home to about 22 million people today.

Genetic and linguistic studies suggest the island’s native Malagasy people are mainly of Indonesian descent. The idea of early Indonesians traveling 3,000 miles to the island intrigued Cox. “It’s a surprisingly long distance to come,” he says. So he used computer modeling to parse the clues, running through 40 million settlement simulations. Cox soon pinpointed one that would explain the DNA patterns evident in Madagascar today.

Surprisingly, the current population descends primarily from just 30 or so Indonesian women who arrived 12 centuries ago [pdf]. His conclusion is supported by prior findings that about 30 percent of Malagasy have the same mitochondrial DNA, which is passed from mother to child—far less diversity than in typical human populations, which share less than 2 percent. “This suggests rapid, recent growth from a very small founder population,” Cox says.

It is unclear how Madagascar’s founding mothers (and the fathers who must have been with them) arrived. Cox proposes seafaring merchants thrown off course, or refugees fleeing political strife; the latter could explain why women, usually not found on trade ships, were on board. Now, Cox plans to explore whether small founding groups are characteristic of other early island settlements, including Hawaii. “There may be general rules for settling islands,” he says.


From wired

Madagascar's first residents could have arrived with a shipwreck



The Malagasy people of Madagascar are genetically fascinating. Despite the island's location just off the coast of Africa, it was only settled relatively recently -- a mere thousand years ago, according to most estimates. Even more surprising is that many of the Malagasy are of Polynesian descent, with the same linguistic and cultural characteristics also found in a small region of southern Borneo, over 7,000km away.

The exact circumstances of how those settlers arrived on the other side of the Indian Ocean has until now been unclear, but surprising analysis of settlement patterns seems to suggest that Malagasy with Polynesian heritage can trace their lineage back to one of only 30 women, who landed on the island roughly 1,200 years ago. According to molecular bioscientist Murray Cox of Massey University in New Zealand, this means that the settlement of Madagascar might have been the result of a one-off event like a shipwreck rather than any deliberate migration.

Discover Magazine reports that the study, published in the Proceedings of the Royal Society, used previous research which had found that 30 percent of Malagasy people shared the same maternal mitochondria. A diverse population of humans would normally share only two percent, by comparison. Cox and his team ran 40 million different simulations of settlement events to see which was the most likely to have given rise to the current genetic patterns on the island, with the most likely result being a one-off settlement of 30 women landing 1,200 years ago. This fits with the evidence that Madagascar's current population of almost 22 million grew rapidly from a small base population over a short period of time.

The implications of such a small base population are intriguing, because it does not suggest any kind of planned mass migration. It could be that Madagascar was settled by accident by a shipwreck -- Cox proposes some kind of refugee ship rather than a merchant vessel, which would be less likely to carry women.

Madagascar was settled by people from what is now Indonesia and, later, by Africans from the eastern kingdoms of the continent -- but the two groups came into conflict as they established towns and cities. The Marina people of the central highlands (of mostly Polynesian heritage) eventually came to dominate the entire island -- including the coastal peoples of African descent -- by the 1800s, but their dominance was brought to an end when the whole of Madagascar was subjugated by the French in 1897.


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