Nature
PUBLISHED
Scientists have discovered the earliest evidence for right-handedness in humanity’s ancestors, thanks to a 1.8 million-year-old fossil recovered from a stream in Tanzania. Belonging to the now extinct species Homo habilis, the specimen consists of an upper jaw, complete with a set of teeth with tell-tale cut marks on them.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.The markings are described in the Journal of Human Evolution as labial striations, meaning they occur on the lip side of the anterior teeth, and slant from the left down to the right. According to the study authors, these markings were most likely to have been made when the teeth’s owner – known by the catchy name OH-56 – was holding a piece of meat between its teeth while pulling it with the left hand and attempting to cut it with a stone tool in the right hand.
This assumption is based on previous experiments in which people were asked to cut food in this way while wearing a mouth-guard, allowing researchers to examine the types of markings made when the stone tools accidentally made contact with the guards.
OH-56 probably scratched his or her teeth while trying to cut a piece of food. David Frayer
The fact that some of us are righties and some of us are lefties may seem like a mundane characteristic, but it is in fact indicative of brain lateralization, whereby different tasks are controlled by separate hemispheres of the brain. Handedness is thought to be regulated by the left hemisphere, which is also the root of our linguistic capabilities and ability to use tools.
Other primates like bonobos and chimps, however, do not display left- or right-handedness, and don’t have the same degree of brain lateralization as humans. Consequently, they aren’t able to use language, and can’t grasp the sorts of complex technologies that humans are masters of.
The fact that OH-56 appears to have been right-handed, however, suggests that Homo habilis may well have had a level of brain lateralization similar to that of humans, and might therefore have had the ability to use language. As such, this discovery may reveal a key piece of the human evolutionary puzzle, highlighting the origins of our intelligence.
However, study co-author David Frayer said in a statement that such assumptions can’t be made without further evidence, explaining that “one specimen does not make an incontrovertible case, but as more research is done and more discoveries are made, we predict that right-handedness, cortical reorganization, and language capacity will be shown to be important components in the origin of our genus.”
