Comparative Study of Brain Ontogeny: Marsupials, Humans and Other Eutherians
Abstract The human brain is commonly considered unique in its growth pattern, especially in its fast growth in early infancy. Consequently, many researchers were encouraged to find peculiarities in the human brain and development which differentiated it from the brains of other animals. In this paper, we argue that the pattern of human brain growth is not different from that of other mammals, both marsupials and eutherians. Thus, our study, challenges the notion of the uniqueness of the human brain and its development indicating that specifically human mental abilities are not a result of brain morphology or size. In order to test our hypothesis we studied the ontogeny of brain weight relative to body weight using pouch young sample of 43 koalas (Phascolarctos cinereus), 28 possums (Trichosurus vulpecula), and 36 tammar wallabies (Macropus eugenii) preserved in a solution of 10 % buffered formalin. We also analysed the growth of brain vs. body size in all eutherian species falling into this group (humans, rhesus monkeys, dogs, cats, rats and mice).