The brains of human beings are different from those of every other species of animal, because all species’ brains have been tuned to their lifestyles through millions of years of evolution.
But what mental functions separate us most from other animals? What makes us human? Answering this question is a continuous quest of philosophy, comparative psychology, and neuroscience.
Our brains are identifiable as uniquely human through their common anatomical features, yet there is a tremendous amount of variability among human brains. Measures of several anatomical features of the cerebral cortex show that human brains are more variable in terms of the shape, size, and thickness of different cortical regions than are those of chimpanzees. Brain size alone in humans can vary up to twofold, and region size commonly varies by this amount.
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The evolutionary history of the human brain is written in the genome, but the uniqueness of each mind is written in its unique and ever-changing synaptic circuitry. It seems that what makes us all human is also what makes us all different. Everyone’s body and everyone’s brain differs from everyone else’s from the moment of birth, and these differences grow as the final shaping of our bodies and brains is done outside the womb and incorporates our individual experiences in the world.
