The human brain has shrunk over time: the cause

The organ would have shrunk about 3,000 years ago. A group of U.S. researchers have speculated that the shrinkage parallels the expansion of collective intelligence in human societies.

About 3,000 years ago, the human brain shrank. That's what U.S. researchers led by Dartmouth College in Hanover have claimed. The team hypothesized that the shrinkage occurred in parallel with the expansion of collective intelligence in human societies s. The study was published in Frontiers in Ecology and Evolution and leads to new insights regarding the evolution of the main organ of people's central nervous system. While it has been documented so far that the brain has increased in size throughout human evolutionary history, there is a tendency to overlook the fact that since the Pleistocene this organ has decreased in size.

The Shrinking Human Brain Study

"A surprising fact about humans today is that our brains are smaller than the brains of our Pleistocene ancestors. Why our brains have shrunk in size has been a great mystery to anthropologists," explained co-author, Jeremy DeSilva, of Dartmouth College. To solve the puzzle, the researchers decided to study historical patterns of human brain evolution and compare their findings with what is known in ant societies.

From analysis of 985 fossil and modern human skulls, the team identified that the human brain increased in size 2.1 million years ago and 1.5 million years ago, during the Pleistocene, but decreased in size about 3.000 years ago, during the Holocene.

Comparison with ant society

Regarding the comparison with ants, the development of computational models of brain size, structure, and energy for some classes of these insects has shown that group-level cognition and division of labor can lead to adaptive variation in brain size. The result would be that within a social group in which knowledge is shared or in which subjects are specialized to perform certain tasks, the brain can reduce its size and become more efficient.

The co-author of the research, James Traniello, of Boston University, explained that although there are significant differences between ant and human societies, "nevertheless, ants also share important aspects of social life with humans, such as group decision making and division of labor, as well as the production of their own food." These similarities, according to scholars, may give us important information about the factors that could have influenced changes in human brain size.

The evolutionary history of humans is complex, and there are many studies trying to understand all its phases. A team from New York has identified what underlies the loss of the tail in humans, while another group of scholars has analyzed what effects climate has on people's body size.

Stefania Bernardini