In anthropology departments, the debate has long simmered: Was it an improvement in manual dexterity or intelligence that allowed our human ancestors to begin making sophisticated stone tools?

According to one group of scientists, figuring out the answer required only a pair of high-tech gloves and a trained craftsman who could make both simple stone knives and more complicated hand axes. The craftsman wore gloves studded with electronic sensors that tracked his his hand movements. Lead researcher Aldo Faisal of Imperial College London found that simple and complex tools required the same amount of dexterity to produce.

“From these results, dexterity can be ruled out, and we can infer it has something to do with the complexity of the task,” says Faisal. Axes are made in several stages, which requires switching between tasks, suggesting that a higher level of complexity is required in the brain. [New Scientist]

Making complex stone tools was part of a huge evolutionary leap for humans, coinciding with the development of language and increased brain power. The axes improved humans’ hunting abilities, and is thought to have led to better nutrition and improved socialization in the form of group hunts and the division of labor.

Human tool-making began over 2 million years ago with Homo habilis, who made delicate stone flakes. It wasn’t until 500,000 years ago that the human ancestor Homo erectus advanced tool-making to the stage of elegant, detailed hand axes. Faisal’s findings suggest that hominid intelligence needed to evolve before they could build better tools. This supports earlier brain imaging work linking complex tool-making to key areas in the right hemisphere of the brain, including language centers like Broca’s area.

“The advance from crude stone tools to elegant handheld axes was a massive technological leap for our early human ancestors. Handheld axes were a more useful tool for defence, hunting and routine work,” said Faisal, whose study appears in the journal PLoS ONE. “Our study reinforces the idea that toolmaking and language evolved together as both required more complex thought, making the end of the lower paleolithic a pivotal time in our history. After this period, early humans left Africa and began to colonise other parts of the world.” [The Guardian]

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Image: PlosONE/Aldo Faisal