Ancient monkeys crossed 100 miles of open ocean to reach North America, study finds

The discovery of seven miniscule monkey teeth during the expansion of the Panama Canal have led scientists to a startling conclusion: an ancient breed of monkey made the journey from South America to North American before the continents were connected.

As Jonathan Bloch, a vertebrate paleontology curator at the Florida Museum of Natural History, and his colleagues reported in the journal Nature, the capuchin-like creatures crossed at least 100 miles (160 km) of open ocean on makeshift rafts approximately 21 million years ago. This means that monkeys had arrived in North America earlier than experts previously believed.

So how did they do it? As the study authors explained to Reuters, they floated across by accident on makeshift rafts made out of vegetation. The species, a previously unknown monkey known as Panamacebus transitus, were likely the only mammal to make this journey, Bloch said, although he noted that giant ground sloths crossed over to North America about 12 million years later.

The paleontologist called this discovery “mind bending”,” telling Reuters that it would be similar to finding the kangaroos and koalas native to Australia living in the modern-day Asian wilderness.

Creatures were medium-sized fruit-eaters related to modern day capuchins

Bloch and his colleagues found the teeth, the largest of which was a molar just one-fifth of an inch (5 mm) in size, from the Las Cascadas Formation in the Panama Canal Basin in Panama. This formation was precisely dated to 20.9 million years ago, they explained, and at this time, Panama represented the southernmost point in the North American continent.

The study authors told Science that they are not certain exactly how large the Panamacebus transitus population was, or how long it might have survived, but they said that the teeth show that the monkeys were medium-sized (weighing about 3 kg) and ate fruit. They have placed the new species in the Cebidae family, a group of Central and South American primates that also includes capuchin and squirrel monkeys, according to the publication.

Bloch said that the discovery “represents the oldest fossil record… of the group that gave rise to all of the living South American monkeys,” and Marcelo Tejedor, a paleontologist researching New World primates at Argentina’s National Patagonian Center in Chubut but who was not part of the study, called the work “fantastic” and said that it “opens up a heap of possibilities we never expected.”

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