A team of researchers has found evidence that challenges the belief that smaller teeth and tool use occurred after early humans developed larger brains. The idea was that early hominins began to make stone tools after their brains had evolved and these tools then led to the evolution of smaller teeth. After studying the evolutionary evidence, a research team has discovered that tool use and shrinking teeth were events that happened before the evolution of large brains. The findings may change our understanding of human evolution. The details are in a paper that was just published in the journal Proceedings of the National Academy of Sciences.
Although there had never been a formal study, many scientists had believed that the large human brain evolved before tool use. This makes sense because tool use is connected with higher intelligence. When early hominins began making and using stone tools, they didn’t need such large teeth for chewing. This caused the earliest humans to begin evolving smaller teeth. The evolutionary connection between the brain and teeth was considered an example of co-evolution, in which each trait evolved based on the evolution of the other trait. There had never been any real research on this topic, however, and some researchers were concerned that it was becoming conventional wisdom with no evidence to back up the theory.
Scientists from the George Washington University’s Center for the Advanced Study of Human Paleobiology compared eight different hominin species, early ancestors and relatives of modern humans. They analyzed data from the human evolutionary tree and picked out species that were rapidly evolving. These species should have been quickly evolving both larger brains and smaller teeth. Instead, the team found that the two traits were evolving at different times throughout human evolution. In some cases, smaller teeth and tool use occurred before the evolution of the large human brain. The team concluded that in the complex evolutionary history of humans, brain size was not directly linked with teeth size or tool use.
The team’s findings provide new insights into early human evolution. Although many scientists assumed that large brains came first, the team’s results show that evolution was a bit more complex. In reality, large brains, small teeth, and tool use were unrelated traits that showed up at different times during evolution.
Gómez-Robles. Brain enlargement and dental reduction were not linked in hominin evolution. Proceedings of the National Academy of Sciences (2017).