UNITED NEWS INTERNATIONAL (UNI) — Earth is now home to four groups of non-human primates that are living in their own Stone Age.

The news outlet New Scientist reported July 2 that a population of white-faced capuchins in Panama is using stone tools to access food.

The monkeys live on the island of Jicarón.

Scientists first noticed them using stone tools in 2004 but it wasn’t until last year that they caught them doing so on camera.

According to New Scientist, this particular population is the only group of monkeys to use stone tools on the island and only a handful of males within this group actually use them.

It’s unclear when the animals first picked up rocks and started bashing them into nuts and shellfish but scientists reportedly think they stumbled upon the discovery by chance.

If so, it could mean our human ancestors did as well an estimated 2.5 million years ago.