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Stable Isotopes in Fossil Hominin Tooth Enamel Suggest a Fundamental Dietary Shift in the Pliocene

Research Laboratory for Archaeology, Dyson Perrins Building, South Parks Road, Oxford OX1 3QY, UK.
Philosophical Transactions of The Royal Society B Biological Sciences (Impact Factor: 7.06). 10/2010; 365(1556):3389-96. DOI: 10.1098/rstb.2010.0059
Source: PubMed

ABSTRACT

Accumulating isotopic evidence from fossil hominin tooth enamel has provided unexpected insights into early hominin dietary ecology. Among the South African australopiths, these data demonstrate significant contributions to the diet of carbon originally fixed by C(4) photosynthesis, consisting of C(4) tropical/savannah grasses and certain sedges, and/or animals eating C(4) foods. Moreover, high-resolution analysis of tooth enamel reveals strong intra-tooth variability in many cases, suggesting seasonal-scale dietary shifts. This pattern is quite unlike that seen in any great apes, even 'savannah' chimpanzees. The overall proportions of C(4) input persisted for well over a million years, even while environments shifted from relatively closed (ca 3 Ma) to open conditions after ca 1.8 Ma. Data from East Africa suggest a more extreme scenario, where results for Paranthropus boisei indicate a diet dominated (approx. 80%) by C(4) plants, in spite of indications from their powerful 'nutcracker' morphology for diets of hard objects. We argue that such evidence for engagement with C(4) food resources may mark a fundamental transition in the evolution of hominin lineages, and that the pattern had antecedents prior to the emergence of Australopithecus africanus. Since new isotopic evidence from Aramis suggests that it was not present in Ardipithecus ramidus at 4.4 Ma, we suggest that the origins lie in the period between 3 and 4 Myr ago.

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    • "However, some early hominins apparently specialized in such foods. The shift away from reliance on C 3 plants such as hard fruits and nuts and the increase in consumption of C 4 foods signals the expansion of early hominins into drier habitats, and the ability to tolerate fluctuations in climate that would otherwise have severely limited the availability of food items (Thorpe et al., 2010). By about 2 Ma, at least one species of the genus Homo became a much faster runner and efficient hunter, and was able to exploit the open grasslands of Africa (Bramble and Lieberman, 2004). "

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    • "Apparently they do not. Isotope analyses imply that P. robustus consumed greater amounts of C 3 sources than P. boisei: it overlaps entirely in its isotope composition with Australopithecus africanus (Sponheimer et al., 2005; Lee-Thorp et al., 2010), but not in microwear texture (Scott et al., 2005). Inspection RI PLFURZHDU WH[WXUHV SURYLGHG E\ *ULQH et al. (2012) reveals P. robustus to be unique amongst extant and extinct primates, i.e., it does not unequivocally cluster with any other extant primate analysed thus far. "
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    ABSTRACT: The dietary ecology of early hominins, particularly East and South African Paranthropus, remains poorly understood. Here I argue that an integrative approach that combines current knowledge on isotope composition, microwear textures, dental morphology and comparative studies on the extant baboon Papio cynocephalus has the potential to shed light on the possible diet(s) of Paranthropus boisei and P. robustus. Baboons eat a variety of C 4 foods, which differ considerably in nutritional value and material properties. East and South African paranthropines apparently spent longer periods of time feeding on similar C 4 foods; their morphology suggests that they exploited opposite ends of the C 4 plant food niche spectrum that is utilised by baboons. Paranthropus boisei consumed predominantly hard brittle foods, while P. robustus fed on hard tough resources. Because of the high nutrional value of some C 4 foods, a shift in dietary preferences from C 3 to C 4 sources need not have been accompanied by an extension of total feeding time. To what extent differences in food selection and time spent feeding on C 4 foods between P. boisei and P. robustus were due to habitat differences between East and South Africa, or constitute true species preferences, needs to be investigated further.
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    • "Plants adapted to the gradual cooling environment of the Neogene with the rise of many C4 lineages in parallel (Christin et al., 2011; Sage et al., 2011), with the grasses in particular predisposed to C4 evolution (Christin et al., 2013). The expansion of C4-dominated savannahs during the cooling latter stages of the Pliocene 2.8e2.4 mya (millions of years ago) is associated with an increase in the consumption of C4 foods in the diet of hominins such as Australopithecus afarensis, reflecting a greater dependence on warm season grasses and sedges as well as C4-grazing animals (Sponheimer and Lee-Thorp, 1999; Sponheimer et al., 2005, 2013; Lee-Thorp et al., 2010; Wynn et al., 2013; Cerling et al., 2013a, b). Whether this shift involved an increase in the direct exploitation of plants is still unknown, but the dietary shift of the time has been associated with major episodes in brain and digestive evolution in the genus Homo (Aiello and Wheeler, 1995). "
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    ABSTRACT: The colonization of the human environment by plants, and the consequent evolution of domesticated forms is increasingly being viewed as a co-evolutionary plant–human process that occurred over a long time period, with evidence for the co-evolutionary relationship between plants and humans reaching ever deeper into the hominin past. This developing view is characterized by a change in emphasis on the drivers of evolution in the case of plants. Rather than individual species being passive recipients of artificial selection pressures and ultimately becoming domesticates, entire plant communities adapted to the human environment. This evolutionary scenario leads to systems level genetic expectations from models that can be explored through ancient DNA and Next Generation Sequencing approaches. Emerging evidence suggests that domesticated genomes fit well with these expectations, with periods of stable complex evolution characterized by large amounts of change associated with relatively small selective value, punctuated by periods in which changes in one-half of the plant–hominin relationship cause rapid, low-complexity adaptation in the other. A corollary of a single plant–hominin co-evolutionary process is that clues about the initiation of the domestication process may well lie deep within the hominin lineage.
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