These actions were replicated during experiments in which participants wore mouthguards. The results indicated that right-slanting striations are made on teeth when material is pulled with the left hand and struck with the right hand. Right-slanting striations are therefore a good indicator of right handedness.
The subject of the new study – an ancient upper jawbone – provides the oldest evidence for right-handedness known in our genus Homo.
The jawbone belonged to one of our earliest human ancestors, Homo habilis (literally, the “handy man”), who roamed Tanzania in Africa around 1.8 million years ago. The jaw was identified at Olduvai Gorge in the Serengeti Plain, which has yielded some of the earliest archaeological traces in the world.
Marks on teeth
The authors of the study noted a number of striations on the front side of the teeth. They used high-powered microscopes and digital cameras to investigate these striations, particularly patterning in their direction.
Interestingly, nearly half of all striations were right-slanting. Right-slanting striations were particularly dominant on four of the front teeth (left and right central incisors, right second incisor and right canine).
This led the authors to argue that most marks were made with the individual’s right hand. They also suggested that the four front teeth with many right-slanting striations were the focus of most processing activities.
The Homo habilis jaw is important as it provides the oldest evidence for right-handedness in the fossil record. But it is also significant as it suggests that a major level of brain organisation had occurred in humans by at least 1.8 million years ago.
This brain development enabled us to master crucial early skills such as stone tool making and potentially also paved the way for language development. Right-handedness therefore means a lot more to us than simply a preference for using the right hand.
Just some food for thought next time you are brushing your teeth, sending a text message or high-fiving someone.