Cranial capacity and neuron number: A critique and proposal

Abstract

Some recent studies correlating cranial capacity with behavioral development and more molecular parameters such as neuron number are critically examined. These studies are found lacking in terms of basic assumptions and empirical support from other studies. In general, it is shown that these studies have overlooked an important aspect of brain evolution in the Primate Order, i.e., reorganization, or the shifting quantitative relationships of subsystems and components of the nervous system. A distinction is made between two approaches to the problem of the evolution of brain and behavior: (1) the “quantitative‐specific” and (2) the “quantitative‐general.” Attempts to derive specificity in terms of estimates of the number of cortical neurons in different pongid and hominid brains are premature unless basic data regarding organizational shifts are known. A supporting argument for the priority of the “quantitative‐general” approach for all levels of the primate nervous system is made. Such a descriptive level is more amenable to synthesis with current neurophysiological knowledge and primate field and laboratory studies than the “quantitative‐specific” approach.