It is thought that handedness have an important role in human growth, with an early study on the earliest indication of right-handedness in the fossil record coming off light on when and why this trait ascended. Fascinatingly, the clues were originating not in our ancient hands, but in our prehistoric teeth.
It is less well known that brain lateralisation, or the dominance of some cognitive processes in one side of the brain, is a distinctive feature of humans, and one associated with improved cognitive ability. Could handedness have played a role in brain lateralisation? Ancient stone tools made and used by our earliest ancestors reveal some clues.
Use of tools
The most primitive stone tools date to 3.3 million years ago, and were found in recent day Kenya, Africa. Early stone tool creation would have required a high level of skill. We know from experimentations have replicated tool-making procedures that the brain's left hemisphere, which is in charge for planning and performance, is active during this process.
While this bond is not straightforward in most cases, handedness and brain lateralization go hand in hand. So, why use teeth to explore handedness? The answer lies in the deficiency of matching left and right arm bones in the fossil data, particularly those belongs to our earliest ancestors. Teeth, on the other hand, tend to survive well in the fossil collections and can preserve scrapes, or "striations", that establish handedness.
Marks on teeth
The authors of the study noted several striations on the front side of the teeth. They used high-powered microscopes and digital cameras to explore these markings, particularly patterning in their path.
Remarkably, nearly half of all patterns were right-slanting. Right-slanting ridges were particularly leading on four of the front teeth.
This brain growth enabled us to master crucial early skills such as stone tool creation and theoretically also paved the way for language progress. Right-handedness therefore means a lot more to us than simply some references for using the right hand.
