Variations in molar enamel thickness among primates

Variation in hominoid molar enamel thickness

“…From these results, Martin proposed that the ancestral hominoid RET condition was thin, as seen in a hylobatid outgroup, and that the ancestral great ape and human condition was thick. Recently, Shellis et al (1998) suggested that, as the total number of teeth sampled increased, extant hominoids showed slightly different average values than those reported by Martin (1983Martin ( , 1985. Shellis et al's chimpanzee sample was reported to show a range of enamel thickness values that is more similar to that of orangutans (intermediate thickness) than to thin-enameled gorilla teeth.…”

“…Martin (1983) suggested that it is more difficult to produce sections without obliquity from distal cusps than from mesial cusps, and did not present data from the distal cusps of his sample (however, Grine and Martin [1988] presented data from five distal sections of Martin's [1983] human sample). Shellis et al (1998) found general agreement between anthropoid regression lines derived from mesial and distal sections, yet their study did not directly compare planes of section. Kono et al (2002) used a three-dimensional analysis to quantify enamel volume in a small sample of human first molars.…”

“…Reported hominoid values from a controlled (physical) plane of section have necessarily been based on small sample sizes (Gantt, 1977;Martin, 1983Martin, , 1985Grine and Martin, 1988;Andrews and Martin, 1991;Macho, 1994;Beynon et al, 1998;Shellis et al, 1998;Grine, 2002;Olejniczak and Martin, 2002;Schwartz et al, 2003;Smith et al, 2003bSmith et al, , 2004Grine, 2005). Previous studies of extant ape molars have produced a maximum reported sample of 17 teeth from seven individuals of a single species (Martin, 1983).…”

“…Previous studies of extant ape molars have produced a maximum reported sample of 17 teeth from seven individuals of a single species (Martin, 1983). Shellis et al (1998) provided enamel thickness data on a wide range of prosimian and anthropoid molars. However, samples of each species were very small and the majority of molar type values were determined from single teeth.…”

Molar development in common chimpanzees (Pan troglodytes)

“…Smith (2004) examined the correlation between developmental variables in this sample, in part to determine if size differences among cusps or molars may explain some of the apparent variation. Bicervical diameter was used as a size scalar, as it has been demonstrated to have a positive relationship with tooth size (and by inference, body mass) (e.g., Martin, 1983;Shellis et al, 1998;Schwartz, 2000;Grine, 2002). Several variables showed positive allometry, including periodicity, number of Retzius lines, and crown formation time.…”