Ok, here's a mystery of science for you: how did lemurs get to

Madagascar? From genetic analysis, we know their ancestors traversed

the 250 miles separating the island from mainland Africa between 50 and

60 million years ago, but how? Land bridge? Swimming (that's a long

paddle)? How about rafts.

It's actually an old idea, one that had been shelved because present

day ocean currents in the Indian Ocean would blow any seafaring

primates back to the continent. But a new look at ancient currents

suggests conditions were right for impromptu voyages between 56 and 34

million years ago. The study was published in a recent issue of Nature (though I first read about it at Laelaps).

Now, these wouldn't have been pleasant journeys — most of the 'rafts'

were just floating pieces of vegetation cast out to sea during a

tropical storm along with their unfortunate passengers. Even in the

best of times, transit aboard one of these rickety vessels would've

been a couple of weeks, and the vast majority of animals likely never

made it.

Still, there's another reason to believe the rafting idea. Other groups

of mammals on Madagascar today like rodents, carnivorans, and so on

appear to have arrived over the course of tens of millions of years. If

they used a land bridge, you'd expect the whole menagerie to arrive more or less at the same time.

Image: Tambako on Flickr