Perikymata spacing and distribution on hominid anterior teeth

We documented the spacing and distribution of perikymata on the buccal enam el surface of fossil hominin anterior teeth with reference to a sample of m odern human and modem great ape teeth. A sample of 27 anterior teeth attrib uted 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 rep licated and sputter-coated with gold to enable reflected light microscopy o f their surface topography. Anterior teeth were then divided into 10 equal divisions of buccal crown height. The total perikymata count in each divisi on of crown height was recorded using a binocular microscope fitted with a vernier micrometer eyepiece. Then the mean number of perikymata per millime ter was calculated for each division. Similar comparative data for a modern sample of 115 unworn human anterior teeth and 30 African great ape anterio r teeth were collected from ground sections. Perikymata counts in each taxo n (together with either known or presumed periodicities of perikymata) were then used to estimate enamel formation times in each division of crown hei ght, for all anterior tooth types combined. The distributions of these esti mates of time taken to form each division of crown height follow the same t rends as the actual perikymata counts and differ between taxa in the same b asic way. The distinction between modern African great apes and fossil homi nins is particularly clear. Finally, we calculated crown formation times fo r each anterior tooth type by summing cuspal and lateral enamel formation t imes. Estimates of average crown formation times in australopiths are short er than those calculated for both modern human and African great ape anteri or teeth. The data presented here provide a better basis for exploring diff erences in perikymata spacing and distribution among fossil hominins, and p rovide 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 oth er. (C) 2001 Wiley-Liss, Inc.