The aim of this book is to review the evolution of the motor and somatosensory cortex in mammals. It begins with a description of the sensory and motor areas present in various species and their respective anatomical and physiological characterisations. It also discusses research carried out by the author based on the cortical and thalamic connections of the somato-motor cortex of a species of opossum found in Brazil, with the aim of gaining a better understanding of the basic cortical organisation of possible mammalian ancestors.