While the rapid increase in brain size is widely recognized as a key factor in human evolution, many studies have focused on understanding the evolutionary patterns and processes behind it. However, studies have yet to distinguish between changes within species and between different hominin species while also considering the impact of body size on these changes.
A new study of human brain evolution led by the University of Reading has found that modern humans, Neanderthals, and other recent relatives on our human family tree evolved bigger brains much more rapidly than earlier species. This overturns long-standing ideas about human brain evolution, suggesting that brain size increased gradually within each ancient human species rather than through sudden leaps between species.
A research team compiled the largest-ever dataset of ancient human fossils, spanning 7 million years, and used advanced computational methods to fill gaps in the fossil record. This provided the most comprehensive view yet of brain size evolution.
Professor Chris Venditti, co-author of the study, explained that their findings challenge the old belief that brain size changed dramatically between species, like upgrading computer models. Instead, the study reveals a gradual, incremental “software update” within each species over millions of years.
Excessive body fat around the middle linked to smaller brain size
This research also debunks the idea that species like Neanderthals were stagnant and unable to adapt, highlighting continuous and gradual change as the main driver of brain size evolution.
Dr Thomas Puschel, lead author now at Oxford University, said: “Big evolutionary changes don’t always need dramatic events. They can happen through small, gradual improvements, much like how we learn and adapt today.”
The researchers identified a notable pattern: while larger-bodied species tended to have bigger brains, the variation in brain size within a species did not always correlate with body size. This suggests that different factors influence brain size evolution over millions of years than those affecting variation within a species, reflecting the complexity of evolutionary pressures on brain size.
How humans evolved to have distinct large, globular shaped brains?
Dr. Joanna Baker, co-author of the study, emphasized that the evolution of large human brains is a central question in human evolution. Their research reveals that the development of significant human brains mainly resulted from gradual changes within individual species over time.
This study was conducted in collaboration with researchers from University of Oxford and Durham University.
Journal Reference:
- Püschel, T. A., Nicholson, S. L., Baker, J., Barton, R. A., & Venditti, C. (2024). Hominin brain size increase has emerged from within-species encephalization. Proceedings of the National Academy of Sciences, 121(49), e2409542121. DOI: 10.1073/pnas.2409542121
