There's a pretty wild theory about how we think monkeys came to inhabit the Americas. And it’s also a weird one, because we think they got there by sailing across the seas.
Our story begins 140 million years ago during the Cretaceous, when the continents of Africa and South America first split through continental drift. This caused the diversification of many species as the South Atlantic Ocean opened, ending any land link between these two locales.
But it wasn’t until 45 million years ago during the Eocene that the first primates, Eosimias, emerged in China. At some point in the following 5 million years, the descendants of these primates called Talahpithecus made their way into Africa.
Here comes the problem. Not too long ago, we discovered monkeys in the New World, the Amazon, dating back to about 36 million years. According to the fossil record, no primates predate these animals in South America.
Then, 21 million years ago, monkeys (Cebidae) sprung up in North America. These two continents would not be connected by land until 3 million years ago, when the Isthmus of Panama arose.
So the question is, how did primates travel around the world when there was no land for them to walk on? The answer, my friends, is they sailed on rafts across the ocean, surviving the elements to thrive in a new land. Primate conquistadors, if you will.
“It is one of the most bizarre examples of what looks like an ocean crossing,” Alan de Queiroz, evolutionary biologist and author of The Monkey's Voyage, told IFLScience. “Initially a lot of people were kind of incredulous, they didn’t think that it was likely that something like a monkey could cross the Atlantic Ocean.”
But that is exactly what it looks like. It explains how we find primate fossils in the most bizarre places. Other explanations, such as land bridges or island hopping, simply come up short when looking at geological history.
An important discovery supporting the raft theory came in 2012 when the Panama Canal was widened. Researchers used this opportunity to excavate the land and discover previously hidden fossils. And they were stunned to find what looked like primate teeth (Perupithecus ucayaliensis) dating back 21 million years.
“We bounced ideas with colleagues, we thought they could be from a bat,” said Jonathan Bloch from the University of Florida in Gainesville, the lead author on the paper describing that finding. “But all of a sudden it clicked, and it was actually a piece of primate. And that was very exciting, because up until this discovery there hadn’t been any primates found on the North American landmass.”