Sequence of emergence of the permanent teeth in Macaca, Pan, Homo, and Australopithecus: Its evolutionary significance

Abstract

There are two main questions about the sequence of emergence of the permanent teeth in humans: 1) Why is there so much variation in sequence within human populations? (2) What is the adaptive or evolutionary significance of emergence sequence? Here, the human condition is considered by comparing us to other living primates and to our evolutionary past 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 individual pairwise sequences (e.g., M I vs. I M ) in the emergence of the permanent dentition are described for N = 110 Macaca nemestrina, and compared to N = 157 Pan troglodytes and ≥6,000 Homo sapiens. In addition, sequences of gingival emergence are reconstructed for Australopithecus and early Homo. Trends observed across 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 drift to later positions in sequence, either by always emerging late in sequence, or by varying in the direction of late emergence. "Augmented sequences" (sequences written with notations about variability) are important in recognizing evolutionary trends; further, they often alter perception of similarities and differences among taxa. Although samples are small, Australopithecus africanus resembles the rapidly developing genera Macaca and Pan more than it resembles Homo sapiens. © 1994 Wiley-Liss, Inc.

Sequences and Timing of Dental Eruption in Semi-Free-Ranging Mandrills (Mandrillus sphinx)

“…A before B or B before A) in each quadrant. Similar matrices have been used to illustrate eruption sequence polymorphisms in humans, macaques and chimpanzees [Smith, 1994] as well as colobine species [Harvati, 2000]. We follow the conventions of Smith [1994], using square brackets to show sequence reversals occurring at a frequency of >15%, and equals signs for those occurring at >40% in augmented sequences.…”

“…Only C M2 occurred at a higher frequency than the 15% cut-off defined as a significant reversal by Smith [1994]. The augmented eruption sequence for female permanent dentition should thus be written M1 I1 I2 [M2 C] P3 P4 M3.…”

“…'Augmented sequences', that include information concerning the occurrence and frequency of sequence variability are particularly important in recognising evolutionary trends and can alter initial conclusions concerning similarities and differences amongst taxa [Smith, 1994]. However, comparative studies of primates are hindered by a lack of dental development data for many species [Smith, 1994;Smith et al, 1994;Godfrey et al, 2001]. Here we describe sequences, sequence variability and timing of tooth emergence for a large sample of semi-free-ranging mandrills (Mandrillus sphinx) and compare this with other life history variables for this species.…”

“…Emergence patterns are also used to age animals [Phillips-Conroy and Jolly, 1988] and to infer life history influences for extinct species [Godfrey et al, 2003;Smith, 1989]. 'Augmented sequences', that include information concerning the occurrence and frequency of sequence variability are particularly important in recognising evolutionary trends and can alter initial conclusions concerning similarities and differences amongst taxa [Smith, 1994]. However, comparative studies of primates are hindered by a lack of dental development data for many species [Smith, 1994;Smith et al, 1994;Godfrey et al, 2001].…”

“…The chronology of tooth emergence is often used to examine the growth and development of individuals and to compare life histories across species [Smith et al, 1994, and references therein; Godfrey et al, 2001;Harvati, 2000]. Emergence patterns are also used to age animals [Phillips-Conroy and Jolly, 1988] and to infer life history influences for extinct species [Godfrey et al, 2003;Smith, 1989].…”