How early human brains expanded over time
How early human brains expanded over time
By Mo Costandi | Published: 2025-02-15 18:00:00 | Source: The Past – Big Think
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Encephalization – the increase in the size of the brain relative to the body – is a key feature of human evolution, but exactly how this process occurred remains unclear. Looking at studies comparing the cranial capacity of early modern humans with other hominin species, some researchers have concluded that brain size gradually grew over time. Others have argued that the human brain develops in spikes separated by long periods.
To complicate matters further, there is confusion about how evolutionary processes, such as the branching of lineages and the splitting of an ancestral species into two distinct species, contributed to the diversity of brain size seen in early humans and other hominins.
now, New search Provides new insights into patterns of brain expansion within and among hominins. The study published in Proceedings of the National Academy of SciencesIt reveals that brain size increased within lineages encompassing a single species, with the fastest expansion occurring in more recent human ancestors.
Brain expansion
Evolutionary anthropologist Thomas Bushell and his team at the University of Oxford have studied fossils from early human ancestors (hominins) dating back 7 million years, creating the most complete data set on brain evolution to date. Since the excavations are incomplete, they used advanced computer models to estimate the missing details.
Their analysis showed that while species with larger bodies often have larger brains, brain size and body mass do not always increase together. Instead, brain size tended to grow gradually within individual species, influenced by a combination of genetic, environmental and behavioral factors rather than by a single cause.
Furthermore, the researchers found that, within individual species, increases in brain development accelerated in more recent lineages.
“The variation we found suggests different intensities and durations of selective pressures within individual hominin lineages, challenging the idea of a single, unified driver of brain evolution,” Bushell told Big Think.
“Our findings indicate an accelerating increase in brain size within species over time, supporting hypotheses proposing a potential coevolutionary feedback loop involving social activity, culture, technology, and/or language.”
These processes may have enhanced some selective pressures, as greater cognitive abilities allowed for more complex behaviors, which in turn were more strongly selected for by larger brains.
“Genetic mutations may have affected the brain’s developmental potential, but it is more likely that a combination of genetic, environmental and behavioral factors interacted to shape the brain differently across species and time,” Bushell added.
Bushell and his colleagues are already conducting additional analyzes of the data set they have assembled.
“We are beginning to integrate environmental and climate predictions to explore how these factors influence brain development,” he says. “Many old hypotheses have linked the brain and climate, but no clear consensus has been reached. Our approach allows us to test some of these ideas more robustly.”
In a recent preprint, Büchel and colleagues published preliminary evidence of this Cooler and more variable temperatures It may have pushed the brain within species by enhancing adaptations that protect against hypothermia.
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