Humans
PUBLISHED
The Palaeolithic archaeological record in Britain captures a rather sudden increase in stone knapping skills around half a million years ago, indicating that a major milestone in human evolution may have been reached during this period. Analyzing the craftsmanship seen on handaxes produced before and after this juncture, researchers suggest that the breakthrough may reflect a cognitive upgrade that might also have led to the development of speech in archaic humans.
According to the study authors, handaxes older than 560,000 years − such as those found at Fordwich in Kent − are “relatively thick, asymmetrical, and irregular edged”, while those appearing from about 480,000 years onwards are “thin, symmetrical, and regular-edged”. Typified by finds at Boxgrove in West Sussex, this latter group are on average 41 percent slimmer than their less-refined precursors.
That’s a pretty significant design update, given that the change took place over a period of just 80,000 years. To put that into perspective, earlier "Oldowan" toolmakers in East Africa required about half a million years to reduce the thickness of their handaxes by just 15 percent.
Based on the flake scars found on the surfaces of the ancient objects, the study authors conclude that this increase in quality resulted from the adoption of innovative techniques like “turning-the-edge” − which involves continually rotating a piece of flint to produce the optimal angle for striking off a flake − as well as the use of soft hammers made of antler or bone.
In a series of experiments, the researchers found that novice flint knappers could easily grasp these concepts but that mastering them was incredibly difficult, and that even after 90 hours of training, modern participants couldn't produce handaxes matching those from Boxgrove.
The authors point out that advanced knapping training has previously been found to “produce changes in brain white matter in the right ventral premotor cortex within modern individuals”. Interestingly, they go on to note that “expanded motor areas of the brain are essential for the fine motor control of the tongue, lips, jaw, and larynx necessary for speech, with the ventral premotor cortex specifically activated in speech.”
The researchers say that Pleistocene hominin remains from Boxgrove are highly similar to those found at Sima de los Huesos in Spain, where 29 Neanderthal-like humans were seemingly dumped inside a deep shaft after being killed by violent blows to the back of their heads around 430,000 years ago.
That episode is a whole other story, but it’s noteworthy that the Sima de los Huesos specimens possessed lingual bones that were conducive to speech, while the structure of their inner ear also appears to have been specialized for hearing spoken language.
We don’t know if the same is true for the ancient English axemakers, but the evidence presented in the new study indicates that their talent for knapping may have gone hand in hand with the ability to talk.
“The pronounced increase in biface knapping skill evident from around half a million years ago in Britain may reflect a broader expansion of motor control, including the ventral premotor cortex, underpinning the human specialisation for vocal communication,” conclude the researchers.
The study is published in the Journal of Archaeological Science: Reports.
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