A capuchin monkey repeatedly smashes one rock into another in Brazil's Serra da Capivara National Park. The other monkey wears the same expression of anyone who's ever had a roommate learning to play the drums. Credit: M. Haslan. Stone tools are arguably the most important artifacts we have in telling the story of human evolution. While they're not as helpful as finding actual bones, the tools are much less fragile and can give researchers a lot of valuable insights. The way a tool was made tells us about the individual's hand strength, for example, and maybe even the toolmaker's cognition and language skills. In the absence of fossils, stone tools can be an important way to document that humans were even present at a site. But what if I told you a new study suggests that it might be bananas to assume sharp-edged stone tools are evidence of hominins? Making stone tools with sharp edges was long thought to be a distinctly Homo skill set. New research, however, has been chipping away at that idea. Last year, for example, researchers announced they'd found stone tools significantly older than our genus. Also in 2015, a separate team studying hand strength in both humans and an earlier hominin, Australopithecus africanus, found that our ancestral kin were capable of the same power grip that allows us to hold hammers (well, most hammers, anyway). And now, researchers have documented monkeys intentionally smashing stones into shapes that look an awful lot like stone tools found at hominin sites around the world. While they're not claiming the monkeys are using the sharp-edged rocks as tools the way hominins did, the researchers are suggesting it might be time for a reappraisal of stone "tools" that archaeologists have long assumed to be hominin-crafted artifacts.
Stone Cold Science
To sum up their paper, published today in Nature, researchers working in eastern Brazil's Serra da Capivara National Park observed wild capuchin monkeys picking up certain types of quartzite stones and intentionally smashing them into other quartzite stones. Analysis of the stones afterward showed that the process created sharp-edged stone flakes which bore striking resemblance, even under a microscope, to other stone flakes which have been attributed to hominins, including members of our own species. While the researchers don't suggest the monkeys are using a hammer with the end goal of creating a sharp-edged stone flake, they do claim that their observations prove that sharp-edged stone flake creation is no longer just a hominin skill.
