'Human-Like' Thinking Evolved 1.8 Million Years Ago, Suggests New Study

Putt said that neuroarchaeologists look to modern humans to understand how pre-human species evolved cognition since the act of thinking — unlike fossilized bones or ancient artifacts — leave no physical trace in the archaeological record.

The methods used to conduct studies on modern humans crafting ancient tools was limited until recently by brain imaging technology. Previous studies depended on placing people within the confines of a functional magnetic resonance imaging machine — essentially a narrow mental tube — to observe their brain activity while watching videos of people crafting tools.

Putt’s study, by contrast, employed more advanced functional near-infrared spectroscopy — a device that resembles a lightweight cap with numerous wires used to shine highly sensitive lasers onto the scalp — to observe brain activity in people as they learned to craft both types of tools with their hands.

In the study, 15 volunteers were taught to craft both types of tools through verbal instruction via videotape. An additional 16 volunteers were shown the same videos without sound to learn toolmaking through nonverbal observation. These experiments were conducted in the lab of John P. Spencer at the University of Iowa, where Putt earned her Ph.D. before joining IU. Spencer is now a faculty member at the University of East Anglia.

The resulting brain scans revealed that visual attention and motor control were required to create the simpler Oldowan tools. A much larger portion of the brain was engaged in the creation of the more complex Acheulian tools, including regions of the brain associated with the integration of visual, auditory and sensorimotor information; the guidance of visual working memory; and higher-order action planning.

“The fact that these more advanced forms of cognition were required to create Acheulean hand axes — but not simpler Oldowan tools — means the date for this more humanlike type of cognition can be pushed back to at least 1.8 million years ago, the earliest these tools are found in the archaeological record,” Putt said. “Strikingly, these parts of the brain are the same areas engaged in modern activities like playing the piano.”

Kevin D. Fryling
Indiana University

Citation: :The functional brain networks that underlie Early Stone Age tool manufacture.” Shelby S. Putt, Sobanawartiny Wijeakumar, Robert G. Franciscus & John P. Spencer.  Nature Human Behaviour 1, Article number: 0102 (2017)  http://dx.doi.org/10.1038/s41562-017-0102