A Darwinian function for the orbital cortex.

The relationship between evolutionary theory and human psychobiology suffers from a lack of bridging theory concerning Darwinian brain functions. This problem is addressed within the context of the theory that the human brain calculates Darwinian strategies for the long-term organization of behavior. This theory of brain function is tested using the literature of abnormal psychology, particularly phenotypes that appear to lack strategic evaluation of fitness outcomes. It is argued that sociopaths lack such "fitness-calculation", and therefore their behavior leads to reduced fitness, notwithstanding the absence of psychiatric pathology. Accidental, surgical, and congenital lesions to the orbital cortex of the frontal lobes can produce similar behavior, suggesting that the orbital cortex is the seat of strategic fitness-calculation. This bridge between Darwinian theory and brain function opens the way for formal theories of human behavior couched in terms of imminent Darwinian calculation.