p. 424. From the Big Bang to the big brain
- Michael O’Shea
‘From the Big Bang to the big brain’ charts the evolutionary history of the nervous system. The ability to sense and act on environmental stimuli exists even in single celled organisms. However, the development of multicellularity and bilateral symmetry in organisms allowed cells to differentiate and specialize. The human brain is immensely complicated, with new systems piled on top of older ones. However, it still develops in a similar way to simpler organisms — from a fluid filled tube. The anterior end of the tube expands into segments which will form the three divisions of the brain. It is the forebrain — and its cerebral cortex — which has given humans their humanity.