Perikymata spacing and distribution on hominid anterior teeth

Abstract

We documented the spacing and distribution of perikymata on the buccal enamel surface of fossil hominin anterior teeth with reference to a sample of modern human and modern great ape teeth. A sample of 27 anterior teeth attributed to Australopithecus (5 to A. afarensis, 22 to A. africanus) and of 33 attributed to Paranthropus (6 to P. boisei, and 27 to P. robustus) were replicated and sputter-coated with gold to enable reflected light microscopy of their surface topography. Anterior teeth were then divided into 10 equal divisions of buccal crown height. The total perikymata count in each division of crown height was recorded using a binocular microscope fitted with a vernier micrometer eyepiece. Then the mean number of perikymata per millimeter was calculated for each division. Similar comparative data for a modern sample of 115 unworn human anterior teeth and 30 African great ape anterior teeth were collected from ground sections. Perikymata counts in each taxon (together with either known or presumed periodicities of perikymata) were then used to estimate enamel formation times in each division of crown height, for all anterior tooth types combined. The distributions of these estimates of time taken to form each division of crown height follow the same trends as the actual perikymata counts and differ between taxa in the same basic way. The distinction between modern African great apes and fossil hominins is particularly clear. Finally, we calculated crown formation times for each anterior tooth type by summing cuspal and lateral enamel formation times. Estimates of average crown formation times in australopiths are shorter than those calculated for both modern human and African great ape anterior teeth. The data presented here provide a better basis for exploring differences in perikymata spacing and distribution among fossil hominins, and provide the first opportunity to describe four specimens attributed to Homo in this context. Preliminary data indicate that differences may exist among the species attributed to early Homo, especially between Homo ergaster and Homo rudolfensis on the one hand, and Homo habilis sensu strico on the other.

Dental development and life history in Anapithecus hernyaki

“…Australopithecus and differs from the condition in Old World monkeys, Paranthropus, and Homo (Beynon and Dean, 1988;Swindler and Meekins, 1991;Dirks, 1998Dirks, , 2003Dean and Reid, 2001;Dirks et al, 2002 (2004)]. Kelley (1997) cited M1 emergence times in various macaque species as being between 16 and 18 months, but only 9.9 months in the much smaller Cercopithecus aethiops.…”

Rapid dental development in a Middle Paleolithic Belgian Neanderthal

“…Although some scholars debate whether Neanderthals had shorter periods of anterior tooth growth than modern humans (6,7), it is known that anterior tooth growth requires more time in great apes than in humans (16) and is variable among human populations (17). This level of variation within and between hominoid species suggests that anterior tooth formation times are not a reliable predictor of life history (6).…”

“…Long-period incremental features on tooth crowns and roots were quantified, the periodicity of long-period lines was determined from an upper first molar, patterns of postnatal developmental stress were calibrated across teeth, and the duration of crown formation and root development was calculated, yielding the age at death. These results were compared with data on living and fossil Homo, including modern humans from Africa and Europe, as well as a recent study of chimpanzee molar formation (8,10,16,17,(28)(29)(30)(31)(32)(33)(34)(35)(36).…”

Anterior tooth growth periods in Neandertals were comparable to those of modern humans

“…Reid and Ferrell (22) found a modal periodicity of 8 and a mean periodicity of 9 in a sample of 49 Danish canines. Continuing histological work on a small sample of fossil human specimens indicates that they also had mean and modal periodicities of 8 or 9 (23). D.G.-S. has observed a histological section from the Tabun II Neandertal (courtesy of M. C. Dean and the Natural History Museum of London), which appears to have a periodicity of 8.…”