Our human lineage evolved larger brains much more quickly than previous species

While the rapid increase in brain size is widely considered 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 taking into account the influence of body size on these changes.

A new study of human brain evolution conducted by the University of Reading has found that modern humans, Neanderthals and other younger relatives in our human family tree developed larger brains much more quickly than earlier species. This upends long-standing ideas about the evolution of the human brain and suggests that brain size increased gradually within each ancient human species, rather than through sudden jumps between species.

A research team has compiled the largest ever dataset of ancient human fossils spanning 7 million years, using advanced computational methods to fill gaps in the fossil record. This provided the most comprehensive insight yet into the evolution of brain size.

Professor Chris Venditti, co-author of the study, explained that tTheir results challenge the old assumption that brain size has changed dramatically between species, for example as computer models are updated. Instead, the study reveals a gradual, incremental “software update” within each species over millions of years.

Excessive body fat around the middle leads to smaller brain size

This research also refutes the idea that species like Neanderthals were stagnant and unable to adapt, and highlights continuous and gradual change as the main driver of brain size evolution.

Dr. Thomas Puschel, now lead author at Oxford University, said: “Major evolutionary changes do not always require dramatic events. They can happen through small, incremental improvements, similar to how we learn and adapt today.”

The researchers identified a striking pattern: While larger-bodied species tended to have larger brains, variation in brain size within a species did not always correlate with body size. This suggests that different factors influence the evolution of brain size over millions of years than those that influence variation within a species, reflecting the complexity of evolutionary pressures on brain size.

How did humans evolve to have a distinctly large, spherical brain?

Dr. Joanna Baker, co-author of the study, emphasized that the development of large human brains is a central question of human evolution. Their research shows that the development of significant human brains is largely due to gradual changes within individual species over time.

This study was conducted in collaboration with researchers at the University of Oxford and Durham University.

Magazine reference:

1. Püschel, TA, Nicholson, SL, Baker, J., Barton, RA, & Venditti, C. (2024). Hominin brain enlargement is due to encephalization within the species. Proceedings of the National Academy of Sciences, 121(49), e2409542121. DOI: 10.1073/pnas.2409542121