In an attempt to understand genetic changes that led to humans and other mammals developing such big brains, researchers found that this variation in brain size is closely associated with changes in gene families.
Evolution resulted in different mammal species experiencing variable expansion in brain size. For a while now, researchers have been trying to understand the genetic changes underlying these extraordinary adaptations. Unfortunately, scientists still haven't been able to fully understand this process by which some species evolved larger brains called encephalization.
With an aim to better understand how brains became larger and more complex in mammals, Dr Humberto Gutierrez from the School of Life Sciences, University of Lincoln, examined the genomes of 39 species of mammals, a press release revealed. He focused on the size of gene families across these species. Gene families are groups of related genes, which share similar characteristics, often linked with common or related biological functions.
Gutierrez speculated that big changes in the size of these gene families are responsible for related species evolving along different paths. He then went on to find a clear link between increased brain size and the expansion of gene families that were responsible for certain biological functions.
"We found that brain size variations are associated with changes in gene number in a large proportion of families of closely related genes," he said in the press statement. "These gene families are preferentially involved in cell communication and cell movement as well as immune functions and are prominently expressed in the human brain. Our results suggest that changes in gene family size may have contributed to the evolution of larger brains in mammals."
Generally, mammals tend to have larger brains compared to their body size. This is another evolutionary adaptation because keeping such a large brain functioning properly requires a lot of energy.
"The brain is an extremely expensive organ consuming a large amount of energy in proportion to its volume, so large brains place severe metabolic demands on animals," Gutierrez explained. "Larger brains also demand higher parental investment. For example, humans require many years of nurturing and care before their brains are fully matured."
The research paper titled "Increased brain size in mammals is associated with size variations in gene families with cell signalling, chemotaxis and immune-related functions" was published in Proceedings of the Royal Society B.
