Editor's Summary

4 February 2010

Madagascar ahoy

Madagascar has a striking and peculiar fauna. Although distantly related to mammals in Africa, the mammals of Madagascar have clearly been evolving in isolation for tens of millions of years. But how did their ancestors get to the island? In 1940 the distinguished palaeontologist George Gaylord Simpson proposed that mammals got there by the blind chance of rafting across from Africa — the 'sweepstakes' hypothesis. This would explain the oddities of the native fauna — except that the ocean currents flow the wrong way, towards Africa, not away from it. But the competing explanation — a direct land connection — is also ruled out because Madagascar was an island by the time the mammals started their evolutionary course. Jason Ali and Matthew Huber present a solution to the problem: a reconstruction of ocean currents as they would have been in the Eocene, more than 50 million years ago, shows that for a brief period the currents did flow west to east, allowing the colonization of Madagascar by rafting.

News and ViewsBiogeography: Washed up in Madagascar

How, when and from where did Madagascar's unique mammalian fauna originate? The idea that the ancestors of that fauna rafted from Africa finds support in innovative simulations of ancient ocean currents.

David W. Krause


LetterMammalian biodiversity on Madagascar controlled by ocean currents

Jason R. Ali & Matthew Huber