Diet and the Evolution of the Earliest Human Ancestors

Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 01/2001; 97(25):13506-11. DOI: 10.1073/pnas.260368897
Source: PubMed


Over the past decade, discussions of the evolution of the earliest human ancestors have focused on the locomotion of the australopithecines. Recent discoveries in a broad range of disciplines have raised important questions about the influence of ecological factors in early human evolution. Here we trace the cranial and dental traits of the early australopithecines through time, to show that between 4.4 million and 2.3 million years ago, the dietary capabilities of the earliest hominids changed dramatically, leaving them well suited for life in a variety of habitats and able to cope with significant changes in resource availability associated with long-term and short-term climatic fluctuations.

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    • "The wear of teeth by small particulates is of great interest to evolutionary biologists because of its utility as an indicator of diet. This interest is manifest in the extensive field of dental microwear [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]. Conventional wisdom has it that hard foods are fractured in compression (normal, axial loading), leaving residual pits on the enamel surface, whereas soft foods are ground down in shear (sliding , translational loading), leaving scratches. "
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    ABSTRACT: We hypothesize that microwear traces in natural tooth enamel can be simulated and quantified using microindentation mechanics. Microcontacts associated with particulates in the oral wear medium are modeled as sharp indenters with fixed semi-apical angle. Distinction is made between markings from static contacts ('pits') and translational contacts ('scratches'). Relations for the forces required to produce contacts of given dimensions are derived, with particle angularity and compliance specifically taken into account so as to distinguish between different abrasives in food sources. Images of patterns made on human enamel with sharp indenters in axial and sliding loading are correlated with theoretical predictions. Special attention is given to threshold conditions for transition from a microplasticity to a microcracking mode, corresponding to 'mild' and 'severe' wear domains. It is demonstrated that the typical microwear trace is generated at loads on the order of 1 N-i.e. much less than the forces exerted in normal biting-attesting to the susceptibility of teeth to wear in everyday mastication, especially in diets with sharp, hard, and large inclusive intrinsic or extraneous particulates. Copyright © 2014. Published by Elsevier Ltd.
    Acta Biomaterialia 12/2014; 14. DOI:10.1016/j.actbio.2014.11.047 · 6.03 Impact Factor
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    • "The focus on plant foods has accelerated in recent years, partly due to the increasing popularity of techniques , such as phytolith and microwear analysis , that are applied exclusively or primarily to document the use of such foods. This is particularly evident in descriptions of hominid diet that mainly limit themselves to postulating only about broad physical categories of plant resources , such as those that are " hard " or " tough " (Teaford and Ungar 2000; Ungar and Sponheimer 2011). Even given the anthropological penchant for healthy debate, this lack of consensus is somewhat surprising, given that workers should be examining essentially the same evidence, and that there now exists an incredible range of analytical techniques (study of carbon enamel isotopes, phytoliths, microwear, and finite elements, among others) that inform on the foods that our ancestors did eat, or at least could have eaten. "
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    ABSTRACT: Beginning with Darwin, some have argued that predation on other vertebrates dates to the earliest stages of hominid evolution, and can explain many uniquely human anatomical and behavioral characters. Other recent workers have focused instead on scavenging, or particular plant foods. Foraging theory suggests that inclusion of any food is influenced by its profitability and distribution within the consumer's habitat. The morphology and likely cognitive abilities of Ardipithecus, Australopithecus, and early Homo suggest that while hunting and scavenging occurred, their profitability generally would have been considerably lower than in extant primates and/or modern human hunter-gatherers. On the other hand, early hominid diet modelers should not focus solely on plant foods, as this overlooks standard functional interpretations of the early hominid dentition, their remarkable demographic success, and the wide range of available food types within their likely day ranges. Any dietary model focusing too narrowly on any one food type or foraging strategy must be viewed with caution. We argue that early hominid diet can best be elucidated by consideration of their entire habitat-specific resource base, and by quantifying the potential profitability and abundance of likely available foods.
    The Quarterly Review of Biology 12/2014; 89(4):319-57. DOI:10.1086/678568 · 4.89 Impact Factor
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    • "Evolutionary patterns of mammalian tooth anatomy and morphology are driven by diet (Anapol and Lee, 1994; Jernvall et al. 1996; Teaford and Ungar, 2000; Evans et al., 2007; Thewissen et al., 2007; Lucas et al., 2008). Thus, comparing the foraging habits of male and female narwhals can potentially provide useful information about the erupted male tusk. "
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    ABSTRACT: The erupted tusk of the narwhal exhibits sensory ability. The hypothesized sensory pathway begins with ocean water entering through cementum channels to a network of patent dentinal tubules extending from the dentinocementum junction to the inner pulpal wall. Circumpulpal sensory structures then signal pulpal nerves terminating near the base of the tusk. The maxillary division of the fifth cranial nerve then transmits this sensory information to the brain. This sensory pathway was first described in published results of patent dentinal tubules, and evidence from dissection of tusk nerve connection via the maxillary division of the fifth cranial nerve to the brain. New evidence presented here indicates that the patent dentinal tubules communicate with open channels through a porous cementum from the ocean environment. The ability of pulpal tissue to react to external stimuli is supported by immunohistochemical detection of neuronal markers in the pulp and gene expression of pulpal sensory nerve tissue. Final confirmation of sensory ability is demonstrated by significant changes in heart rate when alternating solutions of high-salt and fresh water are exposed to the external tusk surface. Additional supporting information for function includes new observations of dentinal tubule networks evident in unerupted tusks, female erupted tusks, and vestigial teeth. New findings of sexual foraging divergence documented by stable isotope and fatty acid results add to the discussion of the functional significance of the narwhal tusk. The combined evidence suggests multiple tusk functions may have driven the tooth organ system's evolutionary development and persistence. Anat Rec, 297:599-617, 2014. © 2014 Wiley Periodicals, Inc.
    The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 04/2014; 297(4):C1. DOI:10.1002/ar.22773 · 1.54 Impact Factor
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