Isotopic evidence for an early shift to C<sub>4</sub>resources by Pliocene hominins in Chad

The enhanced dietary flexibility of early hominins to include consumption of C 4 /crassulacean acid metabolism (CAM) foods (i.e., foods derived from grasses, sedges, and succulents common in tropical savannas and deserts) likely represents a significant ecological and behavioral distinction from both extant great apes and the last common ancestor that we shared with great apes. Here, we use stable carbon isotopic data from 20 samples of Australopithecus afarensis from Hadar and Dikika, Ethiopia (>3.4-2.9 Ma) to show that this species consumed a diet with significant C 4 / CAM foods, differing from its putative ancestor Au. anamensis. Furthermore, there is no temporal trend in the amount of C 4 / CAM food consumption over the age of the samples analyzed, and the amount of C 4 /CAM food intake was highly variable, even within a single narrow stratigraphic interval. As such, Au. afarensis was a key participant in the C 4 /CAM dietary expansion by early australopiths of the middle Pliocene. The middle Pliocene expansion of the eastern African australopith diet to include savannabased foods represents a shift to use of plant food resources that were already abundant in hominin environments for at least 1 million y and sets the stage for dietary differentiation and niche specialization by subsequent hominin taxa.O ne of the traits that distinguishes humans from our closest living relatives, Pan and Gorilla, is the inclusion of significant quantities of C 4 /crassulacean acid metabolism (CAM) foods in the diet. C 4 /CAM plants include grasses and sedges (C 4 ) common in tropical savannas and succulents (CAM) common in deserts. Therefore, the expansion of hominin diets to consume substantial amounts of C 4 /CAM foods signals a major ecological and adaptive divergence from the last common ancestor (LCA) that we shared with African great apes, which mostly occupy closed wooded habitats. C 4 /CAM food consumption is part of a general argument, based on several lines of evidence, that hominin diets diverged from the diets of the LCA during the shift to drier and more open environments in Africa during the Pliocene (1-4). This dietary transition occurred subsequent to the known fossil record of Ardipithecus ramidus from Ethiopia at 4.4 Ma (5), which shows little evidence of C 4 /CAM food consumption. The earliest previously published hominins to evince substantial C 4 /CAM food consumption are Au. africanus at ≤2.7 Ma (2, 6-8) as well as a small, poorly age-constrained (ca. 3.0-3.5 Ma) sample of Au. bahrelghazali from west-central Africa (9). Thus, current evidence places middle Pliocene Au. afarensis, a hominin with an extensive and well-defined stratigraphic range (3.7-3.0 Ma) in Ethiopia and elsewhere in eastern Africa at the crux of this hominin dietary change.In this paper, we use stable isotope analysis to directly investigate the diet of Au. afarensis from the Hadar Formation of Ethiopia. Stable isotope analysis of mammalian tooth enamel is a paleodietary tool that allows one to determine the proportions of dietary ca...

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“…3.0-3.5 Ma) sample of Au. bahrelghazali from west-central Africa (9). Thus, current evidence places middle Pliocene Au.…”

mentioning

confidence: 88%

“…afarensis combined with other data from African early hominins (9,27,36) begin to clarify the timing of increased C 4/ CAM use in the hominin lineage after the LCA shared with chimpanzees. The data from Hadar and Dikika in this paper, combined with data from Kenyanthropus in the Turkana Basin (27) and Au.…”

Section: Giraffa N = 15mentioning

confidence: 99%

Diet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia

Wynn

Sponheimer

Kimbel

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…However, extensive isotopic data from Plio-Pleistocene hominin teeth provide a clear picture of diets in different lineages, temporal trends, and dietary niche partitioning between Pleistocene genera (91)(92)(93)(94)(95)(96). Two early species (4.4-4 Ma), Ardipithecus ramidus and Australopithecus anamensis, are anomalous for their C 3 -dominated diets (−11.6‰ to −8.5‰).…”

mentioning

confidence: 99%

Neogene biomarker record of vegetation change in eastern Africa

Uno

Polissar

Jackson

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

126

103

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The evolution of C4 grassland ecosystems in eastern Africa has been intensely studied because of the potential influence of vegetation on mammalian evolution, including that of our own lineage, hominins. Although a handful of sparse vegetation records exists from middle and early Miocene terrestrial fossil sites, there is no comprehensive record of vegetation through the Neogene. Here we present a vegetation record spanning the Neogene and Quaternary Periods that documents the appearance and subsequent expansion of C4 grasslands in eastern Africa. Carbon isotope ratios from terrestrial plant wax biomarkers deposited in marine sediments indicate constant C3 vegetation from ∼24 Ma to 10 Ma, when C4 grasses first appeared. From this time forward, C4 vegetation increases monotonically to present, with a coherent signal between marine core sites located in the Somali Basin and the Red Sea. The response of mammalian herbivores to the appearance of C4 grasses at 10 Ma is immediate, as evidenced from existing records of mammalian diets from isotopic analyses of tooth enamel. The expansion of C4 vegetation in eastern Africa is broadly mirrored by increasing proportions of C4-based foods in hominin diets, beginning at 3.8 Ma in Australopithecus and, slightly later, Kenyanthropus. This continues into the late Pleistocene in Paranthropus, whereas Homo maintains a flexible diet. The biomarker vegetation record suggests the increase in open, C4 grassland ecosystems over the last 10 Ma may have operated as a selection pressure for traits and behaviors in Homo such as bipedalism, flexible diets, and complex social structure.

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“…Further, there is good evidence that some of our hominin cousins (Australopithecus bahrelghazali, Paranthropus robustus and Australopithecus sediba) were largely plant eaters (Balter et al, 2012;Henry et al, 2012a;Lee-Thorp et al, 2012). Evidence from contemporary gatherer-hunters suggests that the majority of their dietary energy is derived from plants.…”

Section: Meatmentioning

confidence: 99%

Monocultures: A Blight on Human and Planetary Health

Potter¹

2017

Health of People, Places and Planet: Reflections Based on Tony McMichael’s Four Decades of Contribution to Epidemiological Unde

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Naturally occurring ecosystems are highly complex almost everywhere. Human impact on the environment has, over tens of thousands of years, resulted in their transformation and simplification. The rate at which this has occurred has been accelerating with increases in population size and the development of industrial economies. Much of the impact is the result of food-raising practices, but other human choices regarding land and water use, including mining, forestry and the growth of cities, have also contributed.The hallmark of the human footprint is monoculture, a result of deliberate choices in agriculture, the raising of animals for meat and dairy, and forestry, but now appearing, as an unintended by-product of human activity, in the oceans and soil. By definition, monoculture represents a decline of species over some particular area. As monoculture has become the widespread norm in food raising, species decline is occurring almost everywhere. There are other quantifiable, mostly detrimental, changes that extend out from monocultures and their impact on the simplification of ecosystems as chains and nets of causes and consequences. These span an array of intentional human behaviours designed to maintain monocultures and unforeseen outcomes for the planet and its inhabitants. Such inputs and outcomes include:• kidnapping and slavery • distortions of production systems • fold changes over time of consumption of foods and nutrients, with impacts on human behaviour and health • widespread and increasing antibiotic and hormone use • similar increases in pesticide and herbicide use It is not yet clear how we can reverse many of these trends, but monoculture is one of the central problems we need to solve in order to slow the decline of planetary and human health.

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Isotopic evidence for an early shift to C₄resources by Pliocene hominins in Chad

Cited by 108 publications

References 43 publications

Diet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia

Diet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia

Neogene biomarker record of vegetation change in eastern Africa

Monocultures: A Blight on Human and Planetary Health

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Isotopic evidence for an early shift to C4resources by Pliocene hominins in Chad

Cited by 108 publications

References 43 publications

Diet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia

Diet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia

Neogene biomarker record of vegetation change in eastern Africa

Monocultures: A Blight on Human and Planetary Health

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Product

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Isotopic evidence for an early shift to C₄resources by Pliocene hominins in Chad