Engineers expanding the Panama Canal may have just made a huge discovery. Accoeding to a report from Reuters, a recent study reveals that primates made a perilous journey from South America to North America some 21 million years ago.

The stunning discovery reveals that monkeys managed to traverse at least 100 miles of open sea to reach North America long before the isthmus of Panama formed. The discovery of just seven tiny teeth in the bed of the canal reveal that monkeys had been present in North America for far longer than anyone had previously believed.

The teeth came from Panamacebus transitus, a medium-sized species of monkey that was previously undescribed. While it may seem unbelievable that a monkey could traverse open ocean to travel between continents, Jonathan Bloch, a curator of vertebrate paleontology at the Florida Museum of Natural History at the University of Florida says that it was certainly possible.

“Panama represents the southernmost extreme of the North American continent at that time,” he said. “It may have swum across, but this would have required covering a distance of more than 100 miles, a difficult feat for sure. It’s more likely that it unintentionally rafted across on mats of vegetation.”

Bloch says that these monkeys may have been one of the only species to make it to North America before the two continents became joined by land. Scientists know that the Panama isthmus formed roughly 3.5 millions of years ago, but evidence suggests that other South American species, like the giant ground sloths that were once endemic to the continent, made it to North America before the land bridge was actually formed.

The study, published in the journal Nature, reveals that our narrative of the progression of life in North and South America may not be as accurate as once thought.