Preface Flickart 1. How to get excited about teeth 2. The basic structure of the mammalian mouth 3. How the mouth operates 4. Tooth shape 5. Tooth size 6. Tooth wear 7. The evolution of the mammalian dentition Appendix A. Mechanical properties and their measurement: material properties made easy Appendix B. Properties of teeth and potential foods Notes References Index.

https://bilder.buecher.de/zusatz/20/20997/20997265_vorw_1.pdf

Dental Functional Morphology: How Teeth Work

The rise of the hominids as an adaptive shift in fallback foods: plant underground storage organs (USOs) and australopith origins.

The characteristics of scavenging opportunities in the Serengeti National Park and Ngorongoro Crater are here documented and applied to the Plio/Pleistocene East Turkana and Olduvai lake basins. The earliest stone-tool-using, meat-eating hominids are argued to have most regularly encountered abandoned felid kills of medium-sized adult herbivores in riparian woodlands during the dry season, kills from which little flesh but all marrow and head contents could have been obtained. Additionally, it is suggested that they may have encountered large quantities of scavengeable flesh if sabertooth predation was concentrated on large herbivores. Such reconstruction of a possible hominid scavenging niche is considered a prerequisite to the development of criteria for the archaeological recognition of scavenging.

Characteristics of an Early Hominid Scavenging Niche [and Comments and Reply]

Carbon isotope studies of early hominins from southern Africa showed that their diets differed markedly from the diets of extant apes. Only recently, however, has a major influx of isotopic data from eastern Africa allowed for broad taxonomic, temporal, and regional comparisons among hominins. Before 4 Ma, hominins had diets that were dominated by C3 resources and were, in that sense, similar to extant chimpanzees. By about 3.5 Ma, multiple hominin taxa began incorporating 13C-enriched [C4 or crassulacean acid metabolism (CAM)] foods in their diets and had highly variable carbon isotope compositions which are atypical for African mammals. By about 2.5 Ma, Paranthropus in eastern Africa diverged toward C4/CAM specialization and occupied an isotopic niche unknown in catarrhine primates, except in the fossil relations of grass-eating geladas (Theropithecus gelada). At the same time, other taxa (e.g., Australopithecus africanus) continued to have highly mixed and varied C3/C4 diets. Overall, there is a trend toward greater consumption of 13C-enriched foods in early hominins over time, although this trend varies by region. Hominin carbon isotope ratios also increase with postcanine tooth area and mandibular cross-sectional area, which could indicate that these foods played a role in the evolution of australopith masticatory robusticity. The 13C-enriched resources that hominins ate remain unknown and must await additional integration of existing paleodietary proxy data and new research on the distribution, abundance, nutrition, and mechanical properties of C4 (and CAM) plants.

https://www.pnas.org/content/pnas/110/26/10513.full.pdf

Isotopic evidence of early hominin diets

The diet of early human ancestors has received renewed theoretical interest since the discovery of elevated δ13C values in the enamel of Australopithecus africanus and Paranthropus robustus. As a result, the hominin diet is hypothesized to have included C4 grass or the tissues of animals which themselves consumed C4 grass. On mechanical grounds, such a diet is incompatible with the dental morphology and dental microwear of early hominins. Most inferences, particularly for Paranthropus, favor a diet of hard or mechanically resistant foods. This discrepancy has invigorated the longstanding hypothesis that hominins consumed plant underground storage organs (USOs). Plant USOs are attractive candidate foods because many bulbous grasses and cormous sedges use C4 photosynthesis. Yet mechanical data for USOs—or any putative hominin food—are scarcely known. To fill this empirical void we measured the mechanical properties of USOs from 98 plant species from across sub-Saharan Africa. We found that rhizomes were the most resistant to deformation and fracture, followed by tubers, corms, and bulbs. An important result of this study is that corms exhibited low toughness values (mean = 265.0 J m−2) and relatively high Young’s modulus values (mean = 4.9 MPa). This combination of properties fits many descriptions of the hominin diet as consisting of hard-brittle objects. When compared to corms, bulbs are tougher (mean = 325.0 J m−2) and less stiff (mean = 2.5 MPa). Again, this combination of traits resembles dietary inferences, especially for Australopithecus, which is predicted to have consumed soft-tough foods. Lastly, we observed the roasting behavior of Hadza hunter-gatherers and measured the effects of roasting on the toughness on undomesticated tubers. Our results support assumptions that roasting lessens the work of mastication, and, by inference, the cost of digestion. Together these findings provide the first mechanical basis for discussing the adaptive advantages of roasting tubers and the plausibility of USOs in the diet of early hominins.

/pdf/mechanical-properties-of-plant-underground-storage-organs-3ci9913te7.pdf

Brian Maguire

Papers

Wild plant foods of the Makapansgat area: A modern ecosystems analogue for Australopithecus africanus adaptations