Researchers from the University of Nevada and the University of Liverpool examined a long-standing question about brain size in Homo sapiens. John Moores challenged the idea that the move to complex, civilized societies caused brains to shrink, arguing instead that brain size has remained relatively steady since our species emerged. The findings appeared in the journal Boundaries in Ecology and Evolution.
The team analyzed data drawn from more than 1,000 museum skull specimens compiled by a separate group of anthropologists for a 2021 publication. Their analysis suggested that the human brain experienced a notable reduction approximately 3,000 years ago, coinciding with a shift toward more organized urban life and larger social networks.
The researchers behind the new paper expressed surprise that the apparent decline in brain size occurred during a period marked by significant innovations and historical milestones, including the rise of Egypt’s New Kingdom, the development of written Chinese, the legendary Trojan War, and the appearance of the Olmec civilization.
A reexamination of the 2021 dataset indicated that the brain did not shrink 3,000 years ago. Moreover, brain dimensions have shown little change over the past tens of thousands of years. The growth of agriculture and the move towards complex communities occurred at different times across regions, implying that shifts in brain size would have varied in timing. The 2021 data combined populations from the UK, China, Mali, and Algeria.
The 2021 paper proposed that brain shrinkage could reflect the distribution of cognitive tasks within a large group, reducing the need for individuals to retain vast information internally. This idea drew an analogy to evolutionary patterns observed in ant colonies, where decentralization of information serves group efficiency. The new analysis reconsiders that explanation, emphasizing the limited, regionally diverse signals in brain size changes and the importance of methodological context in interpreting skeletal and anatomical data.