It’s a big discovery that is changing how scientists understand how mankind evolved, and why so many of us are right handed. Scientists have found the earliest evidenc eof right handedness that dates back 1.8 million years ago based on an examination of linear markings on the teeth of Homo habilis, an early version of humans.

The fossil had been discovered in Tanzania in Africa back in 2003 in a stream channel of the Olduvai Gorge, an important archaeological site that has yielded many early human remains since it was discovered. An international team of scientists from a number of universities looked at the ridges, which were only on the lip side of the upper front teeth, and saw that most of the cut marks went left down to the right, indicating right-handedness, according to a statement from the University of Kansas.

They believe this indicates that the person used a tool with the right hand to cut food while holding the food in the mouth, and then pulling the food with the left hand.

“We think that tells us something further about lateralization of the brain,” said David Frayer, a KU professor emeritus of anthropology and the lead author of the study. “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.”

“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.