International Journal of Comparative Psychology

A cladistic approach was used to reconstruct the probable changes from the basic sensorimotor system of early mammals to the much more complex system of humans and other anthropoid primates. At the cortical level, early mammals had as few as 4-5 somatosensory areas and possibly no separate motor areas. Early primates already had 7-8 motor areas, and additional higher-order somatosensory areas in lateral and posterior parietal cortex. Anthropoid primates are further distinguished by more serial processing, 4 distinct fields in anterior parietal cortex, and more areas in posterior parietal cortex.