Complex Cognition of Ancient Humans Shaped the Stone Axe

The ability to create a Lower Paleolithic hand axe may just depend on complex cognitive control by the prefrontal cortex, including the "central executive" function of working memory. The findings reveal a bit more about prehistoric humans and show that our ancient ancestors created relatively complex tools for their age.

"For the first time, we've showed a relationship between the degree of prefrontal brain activity, the ability to make technological judgments, and success in actually making stone tools," said Dietrich Stout, study leader, in a news release. "The findings are relevant to ongoing debates about the origins of modern human cognition, and the role of technological and social complexity in brain evolution across species."

Stone tools are created by striking a stone "core" with a piece of bone, antler, or another stone. These tools provide some of the most abundant evidence of human behavioral change over time. Simple Oldowan stone flakes, as an example, date back 2.6 million years and are some of the earliest known tools. The Late Acheulean hand axe, in contrast, goes back 500,000 years.

In this latest study, the researchers recruited six subjects to train in making stone tools, a skill known as "knapping." The subjects' skills were evaluated before and after they trained and practiced. In addition, the volunteers underwent functional magnetic resonance imaging (fMRI) at the beginning, middle and end of the 18-month experiment while they watched videos that showed rotating stone cores marked with colored cues.

"These data suggest that making an Acheulean hand axe is not simply a rote, auto pilot activity of the brain," said Stout. "It requires you to engage in some complicated thinking."

The findings are published in the journal PLOS One.

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