Why Our Brains Are Getting Smaller

As we know, the brain is responsible for almost every function and is also the most intricate organ in the human body. A new study published in Frontiers in Ecology and Evolution helps us understand the brain’s evolution, which concluded with some surprising facts.  

The study confirms that our brains decreased in size nearly 3,000 years ago. Using ants as models to explain why our brains may increase or decrease in size, the researchers in charge concluded that our brain’s varying size might be a reflection of collective intelligence in society. 

Much documentation states how our brains have increased in size throughout evolutionary history, which we’d guess is better than decreasing. However, the lesser-known evidence proves that our brains began to shrink in size around the Holocene era, following the Pleistocene age.

“A surprising fact about humans today is that our brains are smaller compared to the brains of our Pleistocene ancestors. Why our brains have reduced in size has been a big mystery for anthropologists,” explained co-author Dr. Jeremy DeSilva from Dartmouth College in the paper.

On the hunt for answers, a team of researchers from various academic fields banded together to examine the historical patterns of our brain’s evolution, comparing our patterns to those of ant societies.

“A biological anthropologist and a behavioral ecologist and evolutionary neurobiologist began sharing their thoughts on brain evolution and found bridging research on humans and ants might help identify what is possible in nature,” said co-author Dr. James Traniello from Boston University in the paper.

The paper states that the team of researchers implemented a change-point analysis to a dataset of 985 fossil and modern human skulls. They concluded that human brains increased in size roughly 2.1 million years ago and 1.5 million years ago during the Pleistocene era. That said, they found that our brains decreased in size nearly 3,000 years ago in the Holocene era, which surprised the researchers at how recent these changes occurred. 

“Most people are aware that humans have unusually large brains—significantly larger than predicted from our body size. In our deep evolutionary history, human brain size dramatically increased,” said Traniello in the paper. “The reduction in human brain size 3,000 years ago was unexpected.”

Interestingly, the timing around when our brains began to shrink was around the same time that Homosapians began to develop technologically and socially. So they concluded that as we’ve become more socially aware, intelligent, and conscious, our brains shrunk as a result of these drastic external changes.