Evolutionary factors leave their imprint across all life processes; one core event is the organization of the brain. Brains vary with species, with taxa; linking a conception of evolution with brain function required a conception of the nervous system, its core outline, variation and common themes (Swanson, 2000).
The nineteenth-century British neurologist J. Hughlings Jackson formulated a conception of the nervous system that places the brain within evolution; the brain is understood in terms of levels of function. The neocortex represented a crowning achievement, increasing the range of action.
This was, of course, understood for some time; Jackson's conception of the nervous system in the nineteenth century had cortical tissue, the evolutionary mantle of the brain, underlying the selection of options, in which brainstem sites carried out the basic functions. Devolution of function, typically for Jackson, was linked to forebrain damage, thereby limiting capacity and reducing behavioral options; what evolved was the range of opportunities that reflects the corticalization of function.
Of course, the mantle of progress with corticalization of function was at the center of an egocentric human conception of evolution, with social bonds, social history, human invention, rational decision forming being the pillars of social ascent. The march of progress was the conception, both in terms of biological and cultural evolution.