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Newborn: Adult brain ratios in hominid evolution
Author(s) -
Jordaan Harold V. F.
Publication year - 1976
Publication title -
american journal of physical anthropology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.146
H-Index - 119
eISSN - 1096-8644
pISSN - 0002-9483
DOI - 10.1002/ajpa.1330440209
Subject(s) - homo sapiens , allometry , brain size , primate , biology , human brain , australopithecus , population , growth spurt , limiting , physiology , anatomy , demography , neuroscience , medicine , ecology , endocrinology , mechanical engineering , radiology , sociology , anthropology , magnetic resonance imaging , engineering
The ratio of newborn to adult brain size varies widely in primates. These variations provide an index of the different degrees of postnatal brain growth in the different members of the primate order. The uniquely low figure for Homo sapiens indicates a greater degree of postnatal brain growth and therefore postnatal dependence and also a greater need and opportunity for social organisation. An attempt is made to determine the newborn:adult brain ratio in a proto‐human population, Australopithecus africanus . Two possible causes of the reduction of the ratio in hominid evolution are discussed. The first is the limiting confines of the maternal pelvis adapted primarily for orthograde progression rather than parturition. The second concerns the resultant of a set of three paired variables between the members of each pair of which there exists an allometric relationship. These are the relation between brain and body size in the adult, feto‐maternal weight allometry and the relation between newborn brain‐size and birth weight.