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We assess craniometric variation in 153 individually dated human crania from South Africa with the aim of investigating genetic continuity/discontinuity during the Holocene. Evidence from the archaeological record is used to pinpoint likely episodes of genetic discontinuity. Craniometric data are then used to assess the likelihood of genetic change having occurred. Two periods of possible genetic discontinuity are identified: i) c. 4,000 BP, when an increase in overall population size, shifts in site organization and diet, and reduced mobility, were accompanied by reductions in stature; ii) c. 2,000 BP, when the herding of domesticates and the use of pottery vessels were introduced into the region. Results indicate that there was a decrease in cranial size and concomitant size-related changes in craniofacial shape between c.4,000 BP and 3,000 BP. This was followed almost immediately by a recovery in craniofacial size and a return to pre-4,000 BP craniofacial shape at c. 3,000 BP. This recovery continued gradually, extending into the herder period without any major shifts in morphology at 2,000 BP. It is suggested that the fluctuations in craniofacial size/shape were related to changes in environmental factors. Results obtained are consistent with long term continuity in South African Later Stone Age populations during the Holocene.

Keywords AbstractHistorically, predicting ursid feeding behaviour on the basis of morphometric and mechanical analyses has proven difficult. Here, we apply three-dimensional finite element analysis to models representing five extant and one fossil species of bear. The ability to generate high bite forces, and for the skull to sustain them, is present in both the giant panda and the gigantic extinct Agriotherium africanum. Bite forces for A. africanum are the highest predicted for any mammalian carnivore. Our findings do not resolve whether A. africanum was more likely a predator on, or scavenger of, large terrestrial vertebrates, but show that its skull was welladapted to resist the forces generated in either activity. The possibility that A. africanum was adapted to process tough vegetation is discounted. Results suggest that the polar bear is less well-adapted to dispatch large prey than all but one of the five other species considered.

No abstract available

Ecomorphologies are categories of ecological adaptation and function, although intermediates are not always available to shed light on functionality at the transitional stages between them. We examined an intermediate bone-cracking carnivoran ecomorphology, the stem hyaenine Ikelohyaena abronia, using finite element analysis. Skull models of Ikelohyaena, crown hyaenine Crocuta crocuta, and two other hypercarnivores were simulated with mastication and prey apprehension forces. The results obtained show that Ikelohyaena already possessed derived features in skull stress distribution and levels of strain energy, characteristic of the extant bone-cracking Crocuta; however, the estimated bite forces in Ikelohyaena were significantly lower. Prey apprehension simulations showed similar patterns; the low skull strain energy and low bite force of the Ikelohyaena mandible indicate a poor individual ability to take down large prey. The mosaic features of craniodental function in Ikelohyaena suggest that initial evolution of the hyaenid bone-cracking ecomorphology involved skull shape changes that increased stress dissipation, permitting incorporation of more hard food into the diet. Subsequent evolution of larger bite forces was then required to increase the size limit of bones that can be cracked and consumed. This mode of evolution would have allowed transitional hyaenid ecomorphologies to continuously increase the carcass processing ability both during competitive feeding and scavenging throughout their evolution.

The dietary regimes of 15 ungulate species from the middle Pleistocene levels of the hominid-bearing locality of Elandsfontein, South Africa, are investigated using the mesowear technique. Previous studies, using taxonomic analogy, classified twelve of the studied species as grazers (Redunca arundinum, Hippotragus gigas, Hippotragus leucophaeus, Antidorcas recki, Homoiceras antiquus, Damaliscus aff. lunatus, Connochaetes gnou laticornutus, Rabaticerus arambourgi, Damaliscus niro, Damaliscus sp. nov., an unnamed “spiral horn” antelope and Equus capensis), one as a mixed feeder (Taurotragus oryx) and two as browsers (Tragelaphus strepsiceros and Raphicerus melanotis). Although results from mesowear analysis sustain previous dietary classifications in the majority of cases, five species were reclassified. Three species previously classified as grazers, were reclassified as mixed feeders (H. gigas, D. aff. lunatus and R. arambourgi), one previously classified as a grazer, was reclassified as a browser (the “spiral horn” antelope), and one previously classified as a mixed feeder, was reclassified as a browser (T. oryx). While current results broadly support previous reconstructions of the Elandsfontein middle Pleistocene environment as one which included a substantial C3 grassy component, the reclassifications suggest that trees, broad-leaved bush and fynbos were probably more prominent than what was previously thought.

The evolutionary history of chameleons has been predominantly studied through phylogenetic approaches as the fossil register of chameleons is limited and fragmented. The poor state of preservation of these fossils has moreover led to the origin of numerous nomen dubia, and the identification of many chameleon fossils remains uncertain. We here examine chameleon fossil fragments from the Early Pliocene Varswater formation, exposed at the locality of Langebaanweg "E" Quarry along the southwestern coast of South Africa. Our aim was to explore whether these fossil fragments could be assigned to extant genera. To do so, we used geometric morphometric approaches based on microtomographic imaging of extant chameleons as well as the fossil fragments themselves. Our study suggests that the fossils from this deposit most likely represent at least two different forms that may belong to different genera. Most fragments are phenotypically dissimilar from the South African endemic genus Bradypodion and are more similar to other chameleon genera such as Trioceros or Kinyongia. However, close phenetic similarities between some of the fragments and the Seychelles endemic Archaius or the Madagascan genus Furcifer suggest that some of these fragments may not contain enough genus-specific information to allow correct identification. Other fragments such as the parietal fragments appear to contain more genus-specific information, however. Although our data suggest that the fossil diversity of chameleons in South Africa was potentially greater than it is today, this remains to be verified based on other and more complete fragments.

The Carnivora occupy a wide range of feeding niches in concordance with the enormous diversity in their skull and dental form. It is well established that differences in crown morphology are linked to variations in the material properties of the foods ingested and masticated. However, how tooth root form is related to dietary specialization is less well known. In the present study, we investigate the relationship between tooth root morphology and dietary specialization in terrestrial carnivores (canids, felids, hyaenids, and ursids). We specifically address the question of how variation in tooth root surface area is related to bite force potentials as one of the crucial masticatory performance parameters in feeding ecology. We applied computed tomography imaging to reconstruct and quantify dental root surface area in 17 extant carnivore species. Moreover, we computed maximal bite force at several tooth positions based on a dry skull model and assessed the relationship of root surface area to skull size, maximal bite force, food properties, and prey size. We found that postcanine tooth root surface areas corrected for skull size serve as a proxy for bite force potentials and, by extension, dietary specialization in carnivores. Irrespective of taxonomic affinity, species that feed on hard food objects have larger tooth roots than those that eat soft or tough foods. Moreover, carnivores that prey on large animals have larger tooth root surface areas. Our results show that tooth root morphology is a useful indicator of bite force production and allows inferences to be made about dietary ecology in both extant and extinct mammals.