Consider all the theories put forward to explain personality. Freud argued that early family experiences relating to defecation and genital stimulation created unconscious states that influenced behavior through life. In the 1950’s, the common view was that humans begin as nearly blank slates and that behavior is learned through stimulus and response. Over the ages, thinkers have argued that humans are divided between passion and reason, or between the angelic and the demonic.
But now the prevailing view is that brain patterns were established during the millenniums when humans were hunters and gatherers, and we live with the consequences.
This is precisely the rhetorical move Buller's book is concerned with. You start with the notion that the mind/brain is a physical and biological system created by the process of evolution. This is what Buller calls "evolutionary psychology." But then you leap to a rather different notion -- what Buller calls "Evolutionary Psychology" -- that the mind is a massively modular system whose models are adaptations to conditions prevailing during the Pleistocene epoch, i.e. "the millenniums when humans were hunters and gathers" or the "environment of evolutionary adaptadness." Buller's argument, and it's quite convincing so far, is that while the evidence for evolutionary psychology is very strong, the evidence for Evolutionary Psychology is quite weak.