Got it: a macaque prises shellfish from a rock in Thailand Michael Haslam

A CASHEW is a tough nut to crack. You must carefully balance it on an anvil and bash it with a hammer, while avoiding contact with the caustic resin in its shell. This takes great skill. Yet bearded capuchin monkeys living in north-east Brazil take it in their stride. And their tool-wielding talents don’t end there. They also dig for tubers and insects with rocks. Females sometimes even hurl them at males in what appears to be an unusual flirting tactic. We used to think that using tools was the preserve of our hominin lineage and one of the remarkable talents that made us human. So much for that idea…

In fact, we have known for some years that our closest living relatives, chimps, employ a variety of tools, including some made of stone. Recently, primatologists have been intrigued to discover that this also applies to two more-distant cousins – the capuchins and macaques living in a coastal region of Thailand. The findings have attracted the attention of archaeologists keen to explore the so-called Stone Ages of non-human primates. Digging through layers of dirt, they have already unearthed the remains of tools made thousands of years ago.

Their discoveries usher in the new discipline of primate archaeology, which has the potential to give novel insights not just about these species but also about our distant ancestors. Before, it was assumed that we alone possessed an archaeological record containing material evidence of past behaviours. Now that three more such records are emerging, it is possible to make comparisons for …