Five ways that stone-smashing capuchins show that humans aren’t so special
5x5 Capuchin monkeys who smash rocks together have cast doubt on the idea that making tools is unique to humans, and shed light on the inspiration for early tools.
Karl Pilkington will probably turn this into a story about monkeys using Philips screwdrivers to make Ikea furniture, but I see it as another clue that intelligence is a phenomenon that can be measured on a sliding scale across species.
The Brazilian wild bearded capuchin monkeys studied by Tomos Proffitt, an archaeologist at the University of Oxford, weren’t actually making tools to carve wood or cut meat, they were trying to turn the quartz or lichen on the rocks into a dust they could eat.
An unintentional byproduct of the rock-breaking was sharp-edged flakes and broken stone cores, which look like the rocks traditionally interpreted as evidence of early stone technology because they do not happen naturally. The researchers even excavated flaked hammer-stones which would traditionally be considered flaked artefacts, if it wasn’t for the modern-day capuchins merrily making more.
1 Tool-making could have arisen from these accidental flakes The discovery of archaeological sites often accidental, so there are huge gaps in the evolutionary chain from the common ancestors of modern primates and hominids, and where on that chain they started using tools. Prehistoric inventions are often assumed to be as much about opportunity as inspiration, and the capuchins here were seen to re-use broken hammer-stones as fresh hammers, they didn’t use the flakes for cutting or scraping. Maybe they’re not smart enough, but it would only take one early ape-man to pick up a flake and use it for something new.
2 Advanced tools are still exclusive to humans, but how far? The researchers are clear that there’s no suggestion that primates were involved at sites where stone-aged tools have been identified from more than three million years ago. Nevertheless, with evidence of nut-cracking and other tool use among capuchins, as well as evidence of crude stone tool creation among West African chimps in prehistoric times, it’s going to be difficult to claim that advanced tool use is purely human territory. If creating tools to interact with our environment is a characteristic of intelligence, then it starts to look like steps along a scale of how tools are taken from one purpose — cracking rocks and nuts — and applied to another, like scraping meat from bones or the inside of fruit.
3 Is this a cultural behaviour? Proffitt’s not a primatologist, so he’s more interested in whether the stone flakes look like artefacts that archaeologists use to infer tool use by the ancestors of modern humans. Capuchins (the genus Cebus) are a well-studied non-human primate with one of the widest ranges of innovative gestures, cultural behaviours for foraging and food processing, and social rituals among non-ape species.
4 Self-medicating animals are another mystery Mammals are well-known for eating unusual foods that don’t fit their diets — cats who eat grass appear to use it as a dietary supplement. Other animals have been documented eating odd substances with limited nutritional value because they seem to like the taste, have health benefits or even have psychoactive properties (the study is called Zoopharmacognosy). What are the benefits of the the quartz dust or ground-up lichen it contains, do the monkeys learn to eat it or are they following an instinctive knowledge?
5 This is speculative science giving itself a reality check I was surprised to see that Profitt and his team are archaeologists, not primatologists. Popular archaeology shows like Time Team would have you believing in prehistoric stew because they found a few beans, and it’s easy for specialists in fields like paleontology and evolutionary biology to speculate wildly on thin evidence. This research warns paleontologists that they should be careful that their ancient stone flakes are really hominid artefacts, and that it’s important to have a broad awareness of related disciplines.
Michael Haslam, a co-author also from the University of Oxford, told The Guardian: “The fact that we have discovered monkeys can produce the same result does throw a bit of a spanner in the works in our thinking on evolutionary behaviour and how we attribute such artefacts.”
