The discovery of seven small fossilized teeth led to a surprising revelation: 21 million or so years ago, Panamacebus transitus monkeys crossed 100 miles or more of ocean to travel from South America to North America, doing so at a time when the two weren’t connected together by land. The fossilized teeth were found during excavations at the Panama Canal, and pose bigger questions than they answer.
The question, of course, is how the monkeys managed to move the 100 or so miles across the ocean from South to North America. There’s no real answer, though ample speculation: they could have swam, though that is considered very unlikely. Deliberately rafting to their new home is also unlikely. The seemingly most sensible assumption is that they ended up one some sort of floating mass of vegetation and were lucky enough to end up back on land.
The Panamacebus are described as having been medium-sized and similar to the capuchins alive today. The species had previously been unknown to science, and reveals that monkeys had migrated from that landmass to another much, much earlier than researchers had thought — and in a manner that would have been difficult.
At this point, the monkeys are the only known of their kind to travel from South America to what is now known as Panama. Of the teeth that were discovered, some were molars measuring up to a fifth of an inch in length. This voyage was likely only trumped by the assumed oceanic travels of monkeys from Africa to South America about 37 million years ago.