New Delhi: A bigger body does not always necessarily mean a bigger brain, said a research team that found a disproportionate relationship between the two.
For more than a century, scientists have thought that the larger an animal is, the brain is proportionally larger — a "linear" or straight-line relationship, according to the study's authors.
"We now know this is not true. The relationship between brain and body size is a curve, which essentially means that very large animals have smaller brains than expected," said lead author Chris Venditti of the University from Reading, United Kingdom.
The study, published in the journal Nature Ecology and Evolution, revealed a "simple association" between body and brain size across mammals, also allowing researchers to identify species that deviate from the norm.
Humans, who evolve more than 20 times faster than other mammals, are known to have enormous brains compared to their body size and are considered outliers in this regard. Larger brains compared to the body are related to intelligence, being social and complex behaviors.
However, in this study, the authors identified other species that also buck the trend: primates, rodents and carnivores.
In these three groups, there is a tendency for brain size (relative to body) to increase over time, according to the 'Marsh-Lartet' rule. But this is not a universal trend in all mammals, as previously believed, the researchers said.
Although all mammals have shown rapid changes toward both smaller and larger brains, "in larger animals, there is something that prevents the brains from growing too large," according to study co-author Joanna Baker of the University of Reading.
"It remains to be seen whether this is because large brains beyond a certain size are simply too expensive to maintain," Baker said.
"But since we also observed similar curvature in birds, the pattern appears to be a general phenomenon: What causes this 'curious ceiling' applies to animals with very different biology," Baker said.
For example, bats very quickly reduced their brain size when they first emerged, but then the changes in their brain size slowed, suggesting that there may be limits to how large their brains could evolve due to the demands of the flight, the research team said.
For more than a century, scientists have thought that the larger an animal is, the brain is proportionally larger — a "linear" or straight-line relationship, according to the study's authors.
"We now know this is not true. The relationship between brain and body size is a curve, which essentially means that very large animals have smaller brains than expected," said lead author Chris Venditti of the University from Reading, United Kingdom.
The study, published in the journal Nature Ecology and Evolution, revealed a "simple association" between body and brain size across mammals, also allowing researchers to identify species that deviate from the norm.
Humans, who evolve more than 20 times faster than other mammals, are known to have enormous brains compared to their body size and are considered outliers in this regard. Larger brains compared to the body are related to intelligence, being social and complex behaviors.
However, in this study, the authors identified other species that also buck the trend: primates, rodents and carnivores.
In these three groups, there is a tendency for brain size (relative to body) to increase over time, according to the 'Marsh-Lartet' rule. But this is not a universal trend in all mammals, as previously believed, the researchers said.
Although all mammals have shown rapid changes toward both smaller and larger brains, "in larger animals, there is something that prevents the brains from growing too large," according to study co-author Joanna Baker of the University of Reading.
"It remains to be seen whether this is because large brains beyond a certain size are simply too expensive to maintain," Baker said.
"But since we also observed similar curvature in birds, the pattern appears to be a general phenomenon: What causes this 'curious ceiling' applies to animals with very different biology," Baker said.
For example, bats very quickly reduced their brain size when they first emerged, but then the changes in their brain size slowed, suggesting that there may be limits to how large their brains could evolve due to the demands of the flight, the research team said.
