Don’t tell my three-year-old, but throwing rocks may a sign of brain development and the rise of human civilization. Actually, from a parental perspective it’s even worse, because the key behavior that has anthropologists excited was throwing rocks at animals. As a group. Of course, as hominids have evolved, every bit of behavior has, at some point, been cutting edge innovation. While often this is more obvious, such as when stones have been carved into specific tools, sometimes even unremarkable rocks may hint at important milestones in human history.
The key trait about the rocks in question is their quantity and their location. Any individual stone would easily be overlooked, but an unusual collection of egg-sized stones has been found amongst bone beds in the hills of Georgia. 1.8 million years ago, when most of the animal bones were deposited here, the area would have had plenty of large, predatory cats, wolves and hyenas, plus a population of Homo erectus. H. erectus was an ancestor of humans, standing around five feet tall with brains smaller than our own. At this time, nobody was carving tools, but researchers believe the piles of rocks found around animal skeletons indicates that these hominids had at least figured out throwing.
What’s so special about throwing stones?
Throwing a rock doesn’t sound like a big deal at first, especially since other primates more distantly related to humans can throw things as well. The significance is that it appears that these rocks were gathered together on purpose, likely as an ammo cache to be thrown at some of the big cats roaming the area. Just like hyenas and lions in Africa today spend a lot of energy chasing each other off downed prey, clawless and squishy members of H. erectus needed a strategy to defend, or steal, food from other predators. Coordinating a group enough to gather and throw rocks would have required a considerable amount of brain power to pull off.
Beyond the social cooperation of these proto-militias, the physical act of throwing a rock may be tied to brain development as well, specifically around Broca’s area. This region of the brain that helps us manage hand-eye coordination, say for flicking a small stone at a lion, has also been associated with language functions. Throwing rocks didn’t push H. erectus to spoken language, but if we can figure out how coordinated they were, it may help us better estimate how developed their cognitive abilities may have been.
Source: Did Chucking Stones Make Us More Human? by Paul Salopek, National Geographic