The brain size of modern humans increased slowly but surely over the course of three million years, according to a new study. Our brains are said to be more than three times larger than bonobos and chimpanzees, our closest living relatives.
The new study suggests that the gradual increase in brain size was caused by the evolution of larger brains within populations of individual species. While this is believed to have been the main catalyst, researchers also note that the extinction of smaller-brained species and their subsequent replacement by larger-brained species was also a factor.
“Brain size is one of the most obvious traits that makes us human. It’s related to cultural complexity, language, tool making and all these other things that make us unique,” said Andrew Du, PhD, a postdoctoral scholar at the University of Chicago and first author of the study.
Du and his colleagues compared research data on the skull volumes of 94 fossil specimens from 13 different species starting with our earliest human ancestors, Australopithecus, from 3.2 million years ago. Other species included Homo erectus, which is considered a pre-modern species dating back 500 thousand years ago. It was during that time when brain size began to overlap with that of modern humans.
Researchers noticed that brain size increased gradually over three million years once they counted at the groups descending from a common ancestor.
Once they delved deeper into the analysis, they found that the increase was triggered by three different factors. One was the evolution of larger brain sizes within individual species populations, the other was the addition of larger-brained species, and the last was the extinction of smaller-brained species.
The researchers also found that the rate of brain size evolution within hominin lineages was slower than how it operates today.
The study was published in the journal, Proceedings of the Royal Society B.
Image Source: Pexels
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