How do brains evolve complexity? An essay

A case can be made for the proposition that the most neglected aspect of biology is the evolution of complexity and for the assertion that the evolution of complex nervous systems—in short, of the brain—is an outstanding fact, manifesting a span of difference in grade of complexity from the simplest exemplars to the most advanced far greater than any other systems known except systems made up of many brains. The aim of this essay is not to make this case, which I take to be self-evident but to point out how little studied are the specifics defining the grades of complexity, in other words, the consequences of neural evolution. A major step in opening this field of study would be to recognize some way of measuring complexity, relevant to animal biology.