A neurobiologist from the USA has proposed a theory to explain why the human brain has stopped growing in size despite human evolution. He analyzed brain volume data from modern humans and compared it to similar data from ancient Homo species. The study revealed that about 300,000 years ago, the brain's growth began to slow down, and eventually, it stopped altogether.

The researcher examined 800 hominid skulls, including species like Homo erectus, Homo heidelbergensis, Neanderthals, Homo naledi, and Homo rudolfensis. Additionally, he studied the skulls and brain volume of 690 modern humans.

The results showed that approximately 100,000 years ago, human brain growth ceased and has remained almost unchanged since then. However, among early Homo sapiens, individuals with larger brains had better survival chances.

The scientist suggested that the cessation of brain growth might be linked to human adaptation to the changing climate. He believes that Homo sapiens could develop cognitive skills without the need for further brain expansion. With the development of speech, tool usage, and the accumulation of collective knowledge, humans were able to survive in new conditions.

Furthermore, the scientist pointed out that the brain is a major energy consumer. Increasing its size under changing climatic conditions could have jeopardized human survival, as the brain consumes about 20% of the body’s energy even without cognitive load. Therefore, if the brain had continued to grow, it would have been unsustainable to "feed" it.