Monkeys like humans make stone flakes: study

Researchers have observed wild-bearded capuchin monkeys in Brazil deliberately break stones, unintentionally creating flakes that share many of the characteristics of those produced by early Stone Age hominins.
The difference is that the capuchins' flakes are not intentional tools for cutting and scraping, but seem to be the by-product of hammering or 'percussive behaviour' that the monkeys engage in to extract minerals or lichen from the stones, researchers said.
The finding is significant because archaeologists had always understood that the production of multiple stone flakes with characteristics such as conchoidal fractures and sharp cutting edges was a behaviour unique to hominins, they said.

They suggest that scholars may have to refine their criteria for identifying intentionally produced early stone flakes made by hominins, given capuchins have been observed unintentionally making similar tools.
Researchers from the University of Oxford, University College London in the UK and University of Sao Paulo in Brazil observed individual monkeys in Serra da Capivara National Park unintentionally creating fractured flakes and cores.
While hominins made stone flake tools for cutting and butchery tasks, the researchers admit that it is unclear why monkeys perform this behaviour.

They suggest that the capuchins may be trying to extract powdered silicon (known to be an essential trace nutrient) or to remove lichen for some as yet unknown medicinal purpose. At no point did monkeys try to cut or scrape using the flakes.

"Within the last decade, studies have shown that the use and intentional production of sharp-edged flakes are not necessarily linked to early humans (the genus Homo) who are our direct relatives, but instead were used and produced by a wider range of hominins," said lead author Dr Tomos Proffitt, from the School of Archaeology at Oxford.
"However, this study goes one step further in showing that modern primates can produce archaeologically identifiable flakes and cores with features that we thought were unique to hominins.
"This does not mean that the earliest archaeological material in East Africa was not made by hominins. It does, however, raise interesting questions about the possible ways this stone tool technology developed before the earliest examples in the archaeological record appeared," said Proffitt.

These findings also challenge previous ideas about the minimum level of cognitive and morphological complexity required to produce numerous conchoidal flakes.
The monkeys were observed engaging in 'stone on stone percussion', whereby they individually selected rounded quartzite cobbles and then using one or two hands struck the 'hammer-stone' forcefully and repeatedly on quartzite cobbles embedded in a cliff face.
This action crushed the surface and dislodged cobbled stones, and the hand-held 'hammer stones' became unintentionally fractured, leaving an identifiable primate archaeological record.
The research was published in the journal Nature.