Brett Ryder
IN DECEMBER 2016, , Germany, was doing fieldwork in Colombia when something incredible crossed his path. While chugging across a vast expanse of wetland, he passed an . “Have you ever seen a howler monkey?” says Fritz. “They’re huge! But the trees were large enough so the monkeys can permanently live in them. They do not swim.” All told, the island covered an area about the size of two Olympic swimming pools.
Fritz later told a collaborator, Jason Ali at the University of Hong Kong. Ali’s jaw hit the floor. “For me, it was just a random observation,” says Fritz. “But he is the floating island guy. He has worked on them for years, but never seen one.”
Ali is one of the leading advocates of one of the most controversial ideas in evolutionary biology: that the presence of certain species in certain places can only be explained by long-distance maritime voyages. The hypothesis, essentially, is that animals were carried across the ocean on rafts of vegetation and started afresh on the other side.
The sheer unlikeliness – some would say preposterousness – of this idea has always been an obstacle to its acceptance, and the arguments for and against the rafting hypothesis have sloshed back and forth for 160-odd years. But now, with floating islands in Colombia and fresh clues from the sea floor, both sides are claiming to have evidence that could finally see the idea sink or swim.
The rafting hypothesis is as old as the…
