Why has the human brain been shrinking for 3000 years?

A tennis ball is an equivalent in volume of what our brain has lost since Homo sapiens. A 10% shrinkage in its size, which has been questioning the scientific community for decades. Biologists, anthropologists, and neuroscientists at the universities of Dartmouth and Boston may have found the answer. Their study was published in the journal Frontiers in Ecology and Evolution, in October 2021.

Our brain, smaller than Cro-Magnon’s

Over the past 20,000 years, our brain has grown from 1,500 to 1,350 cm3. Cro-Magnon and Homo sapiens had much bigger brains than ours. According to scientists, the decline in its size began about 3,000 years ago, when it entered the Holocene geological era. So what happened?

To try to answer it, the researchers analyzed ants whose community way of life is considerably close to the organization of our human societies.

Collective decision-making, the division of labor, or the manufacture of one’s own food, are all characteristics that we share with these small insects. Similarities that“could globally tell us what factors could influence changes in the volume of the human brain,” the researchers consider.

The fault of collective intelligence?

Verdict? According to their results, we owe the decrease in the size of our brain… to our social systems! In fact, sharing knowledge, and“decision-making at the group level“, has allowed the brain to better manage the collection and sorting of information and thus consume less energy.

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” Humans live in social groups in which several brains contribute to the emergence of collective intelligence,” the neuroscientist comments. And as in our friends the ants, it is the “aspects of sociability”, and“the large size of groups, agrarian life stories, the division of labor and collective cognition”, which are at the origin of the evolution of the human brain.

However, let’s be clear, Cro-magnon was no smarter than us “modern” humans: size does not make intelligence.

boys dressed as businessmen wearing mind reading helmets - human brain 個照片及圖片檔

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