Scientists disprove the main myth about the brain: size does not matter

A new study has shown that brain size does not increase in proportion to body size in large animals. Thus, scientists have disproved a common myth.

The study, which analyzed data from 1500 species, shows that large animals do not have proportionally larger brains. It also emphasizes the rapid evolutionary changes in the size of the gray matter of primates, rodents, and carnivores, ScitechDaily reports.

British researchers from the University of Reading and Durham University have compiled a huge dataset of brain and body sizes from about 1,500 species to clarify controversial questions surrounding the evolution of brain size.

A large creature does not necessarily have a large brain

Most people believe that a larger brain compared to body size is associated with intelligence, sociality, and behavioral complexity, which is why humans have evolved large brains. However, when we look at creatures more primitive than humans, a new study shows that the largest animals do not have proportionally larger brains.

Chris Venditti, lead author of the study and professor at the University of Reading in the UK, said that for more than a century, scientists have assumed that brain size gets proportionally larger in the animal and that this relationship is linear. "Now we know that this is not true. The relationship between brain size and body size is a curve, which essentially means that very large animals have smaller brains than expected," the scientist said.

"Our results help to solve the mysterious complexity of the relationship between brain and body mass. Our model is simple, which means that detailed explanations are no longer needed – relative brain size can be studied using one basic model," added Professor Rob Barton, co-author of the study from Durham University.

The human brain does not confirm the pattern of brain development in other species

The study found a simple relationship between brain size and body size in all mammals. However, there are some outliers among the subjects. Among these exceptions is our human species, Homo sapiens, which has evolved more than 20 times faster than all other mammalian species. This has resulted in the massive brains that characterize humanity today. But humans are not the only species to resist this trend.

All mammalian groups have shown rapid bursts of change, both toward smaller and larger brain sizes. For example, bats had a very rapid decline in brain size when they first appeared. But then bats showed a very slow rate of change in relative brain size, suggesting that possible evolutionary constraints are related to the needs of flight.

Growth of brain size in some mammals

Three groups of animals have experienced the most pronounced rapid change in brain size: primates, rodents, and carnivores. In these three groups, there is a tendency for relative brain size to increase over time. This is not a universal trend for all mammals, as previously thought.

Another co-author of the study from the University of Reading, Dr. Joanna Baker, said their work reveals a big mystery. "In the largest animals, there is something that prevents the brain from getting too big. Whether this is because large brains beyond a certain size are too expensive to maintain remains to be seen. But since we also observe a similar curvature in birds, the pattern seems to be a general phenomenon – what causes this 'curious ceiling' applies to animals with very different biologies," Joanna Baker said.

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