How our brains evolved

Wednesday 18th November: Charles Darwin proposed that the human brain was subject to natural selection, and that it shared a common ancestry with other animals. Today we know a lot more about how the human brain developed, and in an extra Darwin and Beyond event Dr Momna Hedjmadi (above), lecturer in biology at the University of Bath, addressed the BRSLI audience on the subject of Cerebral Evolution, including the question of whether it’s the evolution of a multi-layered brain cortex that makes us the humans we are today, capable of language and higher intelligence. 
Whilst the adult human brain weighs roughly 2% of our overall body weight, around 20% of our energy is required to power it. Throughout the talk, diagrams of the brain structure, along with the neurons and glial cells also found in nervous tissue, clearly demonstrated the complex composition of the brain.  This was further highlighted by the fact that there are a quadrillion (1015) synapses found in the human brain! 
Despite sharing common neural functions with other groups, it is only mammals which have developed a multi-layered cortex.  This, and specifically the development of the neocortex, a part of the brain which is especially evident in higher primates, scientists believe to be responsible for the increased intelligence we associate with human beings.  Uniquely, humans have evolved a complex language consisting of symbols, rather than the signals used by other primates to, for example, signal the presence of land or aerial predators.
Dr Hejmadi used the Stroop test – a series of colours spelt out in lettering differing in colour to that portrayed by the word – to demonstrate how our brains are able to handle mixed and somewhat complex messages, and presented evidence from across the field of neurobiology to substantiate what distinguishes and characterises our brain as humans.  Overall, a fascinating talk on the evolution of the brain, and a clear demonstration of which of its features are associated with the evolution of the characteristics we infer as making us uniquely human.
– Vicky Hunt

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