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Evidence for Right-Handedness in 1.8-Million-Year-Old Fossil

The earliest evidence for right-handedness has been found in a Homo habilis fossil. The findings are published in the Journal of Human Evolution.

Three perspectives of the OH-65 maxilla. a. Palatal view; b. labial view; c. close-up of the two central incisors showing concentration of labial striations. Photo credits: David Frayer, KU.

Three perspectives of the OH-65 maxilla. a. Palatal view; b. labial view; c. close-up of the two central incisors showing concentration of labial striations. Photo credits: David Frayer, KU.

The Homo habilis has been found to be more similar to humans than to apes. The resemblance appears to include handedness as well.

“We already know that Homo habilis had brain lateralization and was more like us than like apes. This extends it to handedness, which is key,” says lead author David Frayer, from the University of Kansas.

The 1.8-million-year-old fossil constitutes the teeth of a Homo habilis: it is, in fact, an intact upper jaw that was found in Tanzania, and has been named OH-65. Small cuts (also known as labial striations which were found on the lip side of the anterior teeth of the jaw) marking the teeth provided evidence for right-handedness. The scratches are visible with the naked eye; their alignment and angulation were measured with the help of a microscope.

Frayer and his team observed the majority of cut marks turning from left down to the right. These marks appear to have been produced as a result of OH-65 cutting food in its mouth with a tool held in its right hand while it was using the left hand to pull.

“Experimental work has shown these scratches were most likely produced when a stone tool was used to process material gripped between the anterior teeth and the tool occasionally struck the labial face leaving a permanent mark on the tooth’s surface,” Frayer said.

The direction of the marks, thus, suggests that the Homo habilis was right-handed. According to Frayer, this is the first evidence hinting at a dominant handed pre-Neanderthal.

These findings can now be extrapolated to dig deeper into other fields. For instance, the researchers explain that right-handedness might be linked with brain organisation and language. Previous research suggests that the use of a dominant hand might be associated with brain reorganisation and the use of tools.

“Handedness and language are controlled by different genetic systems, but there is a weak relationship between the two because both functions originate on the left side of the brain,” he said. “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.”

“We think we have the evidence for brain lateralization, handedness and possibly language, so maybe it all fits together in one picture,” Frayer said.

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