NEW YORK -- Call them knockoffs. Rock-smashing monkeys in Brazil make stone flakes that look a lot like tools made by our ancient ancestors. Scientists watched as Capuchin monkeys in a national park ...

We lost them along the way, but our relatives still retain them for balance. Discover the primates with the longest tails.

A capuchin monkey in Costa Rica. Scientists studying the stone-smashing habits of bearded capuchin monkeys in Brazil have found that the primates inadvertently produce stone flakes that look very ...

Kanzi was not the first great ape to learn how to communicate with humans using symbols. Koko the gorilla and Washoe the chimpanzee learned signs that were adapted from American Sign Language. But ...

Hundreds of stone tools discovered in Kenya have revealed that human relatives traveled long distances to find raw material.