Brain’s Asymmetrical Shape May Reflect Human Ability to Adapt

You’ve heard about the right and left brain; in fact, you may have even taken a quiz to find out which side is dominant in you.

But were you aware that the brain is asymmetrical both in its function and its shape? A new US MRI study, entitled Increased morphological asymmetry, evolvability and plasticity in human brain evolution has found that this lopsidedness–clearly visible when viewing MRI brain images–may be the key to the ever-evolving adaptability of the human species.

Lead researcher Aida Gomez-Robles and her team used MRI to look at the brains of 72 chimpanzees (23 male and 49 female) and 73 human (27 male and 46 female), finding structural asymmetries in both, but in humans more so than the chimps.

“It’s very common that there are some areas that are bigger in the left hemisphere than inthe right hemisphere,” says Gomez-Robles. The left brain is known as the creative side of the brain, ruling over cerebral processes like language and expression. Conversely, the right brain is known as the logical side, ruling over processes such as spatial reasoning.

The study outlines three patterns of brain asymmetry:

Directional asymmetry – when a population has brains which consistently feature one side that is bigger than the other

Anti-symmetry – when a population has some individuals whose brains are larger on one side, and some individuals whose brains are larger on the other side.

Fluctuating symmetry – when a population exhibits deviations from average brain shapes–in both halves of the brain. The researchers believe that fluctuating symmetry results from environmental and sociological factors affecting the brain’s development.

“We know that plasticity is an important trait in the function of the brain which is critical for human cognitive evolution,” says Gomez-Robles.

This flexibility–which humans and chimpanzees share, albeit humans more so–allows the brain to adapt to the ever-changing conditions of the environment.