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.
In a paper, published in Nature, the research team says this 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. The paper suggests 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.
The research is authored by researchers from the University of Oxford, University College London and University of São Paulo in Brazil. The team 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 the monkeys try to cut or scrape using the flakes, says the study.
Lead author Dr Tomos Proffitt, from the School of Archaeology at the University of Oxford, comments: ‘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. 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.