Stone flakes made by modern monkeys trigger big questions about early humans

Macaques use stones as hammers to smash open food items like shellfish and nuts. (Lydia V. Luncz)

When monkeys in Thailand use stones as hammers and anvils to help them crack open nuts, they often accidentally create sharp flakes of rock that look like the stone cutting tools made by early humans.

This surprising discovery, described in the journal Science Advances, has archaeologists wondering if they need to rethink their assumptions about some of the stone artifacts produced by early human ancestors over a million years ago.