Primate archaeology is a new and unusual-sounding field, but it has revealed ancient evidence of some clever and dextrous monkey culture.

Researchers from Oxford University, working in Brazil, found ancient "nut-cracking tools" - 700-year-old stone hammers that capuchin monkeys used to open cashew nuts.

One of the researchers, Dr Lydia Luncz, explains how the team found evidence of these "Stone Age monkeys".

Footage of capuchin monkeys courtesy of Tiago Falotico

Video by Victoria Gill