Professor Bruce Bradley with Stone Age tools. See video footage of Professor Bradley flintknapping on BBC Today website.

Stone Age humans needed more brain power for tool design

Stone Age humans were only able to develop relatively advanced tools after their brains evolved a greater capacity for complex thought, according to a new study investigating why it took early humans almost two million years to move from a razor-sharp stones to a hand-held stone axe.

Tiny sensors embedded in gloves and computer modelling were used to evaluate the complex hand skills that early humans needed in order to make two types of tools. This process of tool making began 2.5 million years ago during the Lower Palaeolithic period. The research provides evidence of how the human brain and human behaviour evolved during the Lower Palaeolithic period by comparing the manufacturing techniques used for both Stone Age tools.

Archaeologists from the University of Exeter worked with a cross-disciplinary team, involving researchers from Imperial College London, Emory University, Gotland University College. Professor Bradley of Exeter, a specialist ‘flintknapper’, faithfully replicated ancient tool-making techniques. This is the first time that neuroscientists, archaeologists, anthropologists and a flintknapper have teamed together, using cutting edge technology including data glove sensors and advanced modelling, to develop a deeper understanding of early human evolution.

Neuroscientist Dr Aldo Faisal, the lead author of the study at Imperial College London, said 'The advance from crude stone tools to elegant hand-held axes was a massive technological leap for our early human ancestors. Hand-held axes were a more useful tool for defence, hunting and routine work. Our study reinforces the idea that tool making and language evolved together as both required more complex thought, making the end of the Lower Palaeolithic a pivotal time in our history. After this period, early humans left Africa and began to colonise other parts of the world.'

Prior to this study, there have been different theories about why it took early humans more than 2 million years to develop stone axes. It has been suggested that early humans may have had underdeveloped motor skills or abilities, while others have suggested that it took human brains this time to develop more complex thoughts, in order to dream up better tool designs or think about enhanced manufacturing techniques. Today’s study provides evidence that confirms that the evolution of the early human brain was behind the development of the hand-held axe. It also provides evidence that the advancement of hand-held axe production may have coincided with the development of language, as these functions overlap in the same regions of the modern and early human brains.

The ‘flintknapper’ created two types tools including the razor-sharp flakes and hand-held axes. He wore a data glove with sensors enmeshed into its fabric to record hand and arm movements during the production of these tools.

Professor Bruce Bradley, Archaeologist at the University of Exeter said ‘We discovered that both flake and hand-held axe manufacturing techniques required the same kind of hand and arm dexterity. This enabled us to rule out motor skills as the principal factor for enabling stone tool development.’

The axe-tool required a high level of processing in overlapping areas of the brain that are responsible for a range of different functions including vocal cords and complex hand gestures.

In the future, the team plan to use their technology to include Neanderthal knapping techniques that were current in Eurasia between 150,000 to 35,000 years ago, to glean insights into their brain development.

Date: 4 November 2010