A Phylogenetic Analysis of Behavioral Neuro-ontogeny in Precocial and Nonprecocial Mammals.

Studies of the postnatal development of two groups of mammals are discussed in relation to behavioral change correlated with neurophysiological and anatomical data. The precocial mammals include especially the ruminants (sheep, cow; also horse and guineapig) while the nonprecocial mammals, which require a long period of nursing, include man and the primates, carnivores and rodents. Common features of certain neurological aspects of development are closely compared in this latter group to emphasize the importance of selected age studies to give correlative data from a wide variety of altricious species. For example, the relative age of a 1-2 week old mouse is equivalent to a 3-4 week old dog or 3 months in man in some behavioral features. The postnatal development of these several species is closely paralleled, but common features of the mother-offspring relationship, especially in dog and man, are not seen in the precocial mammals which are physiologically more independent at birth. These observations indicate that in the field of comparative medicine there is much to contribute by interpolating and extrapolating correlative data from different species. Some of this data in the neurologic field has been brought together in this paper, for especially in developmental and pediatric studies it is desirable to have cross-species data on relative postnatal ages in relation to the degree of maturity of the organism.