Summary: A new study reveals that modern humans, Neanderthals, and other relatives evolved larger brains through gradual changes within each species, overturning the idea of sudden leaps in brain size. Researchers used the largest-ever fossil dataset spanning 7 million years and advanced statistical methods to reconstruct brain size evolution.
They found no consistent correlation between brain and body size within species, highlighting the unique evolutionary pressures shaping brain growth. This research challenges long-standing views and underscores the steady, incremental nature of human brain evolution.
Key Facts:
- Brain size evolved gradually within species, not through sudden leaps.
- The study analyzed fossils spanning 7 million years using advanced methods.
- Brain size evolution was shaped by complex factors beyond body size.
Source: University of Reading
Modern humans, Neanderthals, and other recent relatives on our human family tree evolved bigger brains much more rapidly than earlier species, a new study of human brain evolution has found.
The study, published today (Tuesday, 26 November) in the journal PNAS, overturns long-standing ideas about human brain evolution. Scientists from the University of Reading, the University of Oxford and Durham University found that brain size increased gradually within each ancient human species rather than through sudden leaps between species.
The team assembled the largest-ever dataset of ancient human fossils spanning 7 million years and used advanced computational and statistical methods to account for gaps in the fossil record. These innovative approaches provided the most comprehensive view yet of how brain size evolved over time.
Professor Chris Venditti, co-author of the study from the University of Reading, said: “This study completely changes our understanding of how human brains evolved. It was previously thought that brain size jumps dramatically between species, like new upgrades between the latest computer models.
“Our study instead shows a steady, incremental ‘software update’ happening within each species over millions of years.”
The research challenges old ideas that some species, like Neanderthals, were unchanging and unable to adapt and instead highlights gradual and continuous change as the driving force behind 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 over time, much like how we learn and adapt today.”
Brains, bodies, and evolutionary scale
The researchers also uncovered a striking pattern: while larger-bodied species generally had bigger brains, the variation observed within an individual species did not consistently correlate with body size.
Brain size evolution across long evolutionary timescales extending millions of years is therefore shaped by different factors to those observed within individual species – highlighting the complexity of evolutionary pressures on brain size.
Dr Joanna Baker, co-author from the University of Reading, said: “Why and how humans evolved large brains is a central question in human evolution. By studying brain and body size in various species over millions of years, we reveal that our hallmark large brains arose primarily from gradual changes within individual species.”
Funding: The study was produced as part of a £1 million Research Leadership Awards grant from the Leverhulme Trust. The project was to better understand the evolution of human ancestors.
About this evolutionary neuroscience research news
Author: Ollie Sirrell
Source: University of Reading
Contact: Ollie Sirrell – University of Reading
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Hominin brain size increase has emerged from within-species encephalization” by Chris Venditti et al. PNAS
Abstract
Hominin brain size increase has emerged from within-species encephalization
The fact that rapid brain size increase was clearly a key aspect of human evolution has prompted many studies focusing on this phenomenon, and many suggestions as to the underlying evolutionary patterns and processes.
No study to date has however separated out the contributions of change through time within vs. between hominin species while simultaneously incorporating effects of body size.
Using a phylogenetic approach never applied before to paleoanthropological data, we show that relative brain size increase across ~7 My of hominin evolution arose from increases within individual species which account for an observed overall increase in relative brain size.
Variation among species in brain size after accounting for this effect is associated with body mass differences but not time.
In addition, our analysis also reveals that the within-species trend escalated in more recent lineages, implying an overall pattern of accelerating relative brain size increase through time.
