Long ago, about 36 million years before today, a raft of monkeys found themselves adrift in the Atlantic. They’d been blown out to sea by an intense storm that had ripped up the African coast, and now a mat of floating vegetation was the closest thing to land for miles in all directions. But luck was with them. Thanks to a favorable current, they were thrown onto the beach of a new continent – South America.

I’ll admit that this scenario requires a little scientifically-informed imagination. No one has ever found a fossilized huddle of monkeys clinging to battered vegetation in ancient ocean sediments. But we know that such events must have happened in the past. Teeth tell the tale.

In the latest issue of Nature, paleontologist Mariano Bond and colleagues describe a handful of fossil teeth found in the rainforest of Peru. Some are mysteries, too incomplete to identify down to genus or species, but a set of three molars are clearly from a new species of early monkey.

Three teeth might not seem like much to name a new animal, but, fortunately for paleontologists, mammals have always had very distinct teeth that tend to get fossilized even when the rest of the body decays. From the cusps and ridges, Bond and coauthors were able to narrow down the identity of this animal to a monkey that was about the size of a modern day tamarin. They’ve named it Perupithecus ucayaliensis.

At about 36 million years old, Perupithecus pushes back the arrival of monkeys on South America 10 million years earlier than previously thought. And even better, the molars of Perupithecus closely resemble those of Talahpithecus – an early monkey that lived around the same time in northern Africa. This doesn’t mean that Perupithecus was directly descended from Talahpithecus. Rather, it’s a another strong sign that the ancestors of New World monkeys were accidental migrants from Africa.

Perupithecus, or its immediate ancestors, probably arrived on rafts of storm-tossed vegetation. There wasn’t an overland route for the primates to make the same journey. Even though South America and Africa were once connected, they had drifted apart by 110 million years ago – long before the evolution of primates, much less monkeys. South America stayed an island continent from then until its collision with Panama about 3 million years ago. There was no other way from monkeys to get from Africa to South America except by sea. The monkeys that thrive in the Americas today, from tamarins to muriquis, are the descendants of prehistoric primates fortunate enough to survive the journey.

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