Over time, brain size has increased dramatically. It has become more specialized, plastic and hierarchical than the brain of any other species. Because of this, humans are able to adapt to many different kinds of environments, learn new skills and survive in a changing world.
Increase in the Brain Size
In a study published in the Trends in Neuroscience journal in October 2008, Dr. Eric J. Vallender and colleagues state that the volume of the human brain is three times larger than before the divergence from chimpanzees. This intense increase in brain volume is quite pronounced in the cerebral cortex, and especially in the prefrontal cortical areas. This has resulted in humans having a bigger brain size than that of any other animal relative to their body size. However, according to Dr. Jane Bradbury, this comes with a cost. In her study published in the PLoS Biology journal in March 2005, she says the large brain size is a metabolic drain on a human body.
Increase in Specialization
The bigger the brain gets, the longer it takes to get information from one place to another. According to Dr. Bradbury, the human brain tried to solve this problem by doing things locally and avoiding the communication between two faraway locations, such as locations in different hemispheres. As a result, human brain specialized, and different parts of the brains started to do different things.
Increase in Hierarchy
The centralized, specialized brain also became more hierarchical over time. The newer additions to the brain begin to control the old ones. Little by little cortex, and especially the frontal areas of the cortex, began to control the rest of the brain. This is understandable because the frontal parts of the brain are combining information from the rest of the brain and interpreting it.
Increase in Complexity
The human brain has also evolved in complexity. The number of different parts has increased, and there is much more variety in human brains now than before. For example, as compared to simpler species, mammals developed such new brain structures as neocerebellum and neocortex, says the University of Illinois at Urbana-Champaign.
Increase in the Plasticity
The brain's ability to learn from experience and modify its functions according to them is called plasticity. According to the University of Illinois at Urbana-Champaign, human brain is highly plastic. This allows humans to adjust to different environments and learn new skills. However, the rapid increase in brain plasticity also resulted in prolonged immaturity and development. Human children need constant care and guidance for a long time. Animals that do not have high brain plasticity and that rely mostly on reflexes become independent at a much younger age.
References
- University of Illinois At Urbana-Champaign: Brain Evolution and Development
- Howard Hughes Medical Institute: Human Brain Evolution Was a Special Event
- "PLoS Biology Journal"; Molecular Insights into Human Brain Evolution; Jane Bradbury; March 2005
- "Trends in Neurosciences Journal"; Genetic Basis of Human Brain Evolution; Eric J. Vallender et al.; October 2008
