The human brain has nearly quadrupled in size in the six million years since our species last shared a common ancestor with chimpanzees. However, studies show this trend toward larger brains has reversed in Homo sapiens. In our species, average brain sizes have shrunk over the course of the last 100,000 years.
However, the trend for brain enlargement over time was turned on its head with the arrival of modern humans. The skulls of men and women today are on average 12.7% smaller than that of Homo sapiens who lived during the last ice age.
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So how can we explain this striking reduction? [Ian Tattersall, a paleoanthropologist and curator emeritus with the American Museum of Natural History in New York City] suggests that the shrinkage in brain size began around 100,000 years ago, which corresponds to a period of time in which humans switched from a more intuitive style of thinking to what he terms “symbolic information processing” – or thinking in a more abstract way to better understand your surroundings.
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Tattersall believes that the catalyst that caused this change in thinking style was the spontaneous invention of language. This led to the neural pathways of the brain being reorganised in a more metabolically efficient way, allowing humans to get more “bang for their buck”.
