SEQUENCE OF EMERGENCE OF THE PERMANENT TEETH IN MACACA, PAN, HOMO, AND AUSTRALOPITHECUS - ITS EVOLUTIONARY SIGNIFICANCE

There are two main questions about the sequence of emergence of the pe rmanent teeth in humans: 1) Why is there so much variation in sequence within human populations? (2) What is the adaptive or evolutionary si gnificance of emergence sequence? Here, the human condition is conside red by comparing us to other living primates and to our evolutionary p ast and considered in the light of Schultz's hypothesis that sequence of tooth emergence is adapted to rate of postnatal growth (Schultz AH, In JM Tanner (ed.) Human Growth, pp 1-20, 1960). Frequencies of indiv idual pairwise sequences (e.g., M(1)I(1) vs. I(1)M(1)) in the emergenc e of the permanent dentition are described for N = 110 Macaca nemestri na, and compared to N = 157 Pan troglodytes and greater than or equal to 6,000 Home sapiens. In addition, sequences of gingival emergence ar e reconstructed for Australopithecus and early Homo. Trends observed a cross these catarrhine primates suggest that sequence and variability in sequence can be understood by a simple model of adaptation of tooth emergence to growth rate. As rate of postnatal growth slows, molars d rift to later positions in sequence, either by always emerging late in sequence, or by varying in the direction of late emergence. ''Augment ed sequences'' (sequences written with notations about variability) ar e important in recognizing evolutionary trends; further, they often al ter perception of similarities and differences among taxa. Although sa mples are small, Australopithecus africanus resembles the rapidly deve loping genera Macaca and Pan more than it resembles Home sapiens. (C) 1994 Wiley-Liss, Inc.