“In 1492 Columbus sailed the ocean blue.” That much everybody knows for sure.
Earlier transatlantic travellers may have beaten him to it, of course: the Vikings almost certainly made the crossing, and there are claims that the Egyptians and all manner of other groups did too. But if most of these pre-Columbian ocean voyages sound outlandish and unlikely, they are nothing compared to a transatlantic journey that appears to have taken place about 40 million years ago.
Midway through the Eocene, a crew of monkeys sailed the ocean, er, green.
Like later primates including Christopher Columbus and Leif Ericson, this intrepid band set off in search of glory and riches on the other side of the ocean. Well, sort of.
The evolutionary history of primates has received plenty of scientific attention over the years. This is unsurprising: their history is our history, and in the course of investigating humanity’s roots, researchers have revealed a lot about our distant ancestors too.
We know, for example, that primates probably have their origins in Asia, and thanks to the latest sophisticated studieswe also have fairly accurate estimates for when different groups and species appeared.
One thing that has consistently baffled researchers, however, is how primates arrived in South America.
Geological rumblings in the 1950s and 1960s seemed to provide an explanation. This was when ideas of continental drift and plate tectonics were refined. The phenomenon soon became a catch-all explanation for many of the Earth’s more incongruous species distributions.
In the case of the monkey puzzle the reasoning was simple. In the distant past there was no Atlantic Ocean – Africa and South America formed part of a much larger landmass called Gondwana. So the primitive precursor species of Old World and New World monkeys could literally have walked – or swung – to what is now South America’s east coast.
But molecular clock estimates now date the last common ancestor for New and Old World monkeys to a time about 100 million years after the continents had split apart. So that idea has gone out the window.
Scientists considered alternative theories. Perhaps the monkeys crossed from places other than Africa – via North America, for example, or even through Antarctica. But there are no fossils to support these ideas, despite the primate fossil record being one of the most complete of all major mammalian groups. These ideas do not really stand up to scrutiny.
Unlikely though it sounds, the monkeys simply have to have crossed the Atlantic. Last year, new evidence emerged that reignited the debate and pushed this transatlantic crossing theory to the forefront.