The carbon isotope ecology and diet of Australopithecus africanus at Sterkfontein, South Africa

189

178

Hominin fossil evidence in the Turkana Basin in Kenya from ca . 4.1 to 1.4 Ma samples two archaic early hominin genera and records some of the early evolutionary history of Paranthropus and Homo . Stable carbon isotopes in fossil tooth enamel are used to estimate the fraction of diet derived from C 3 or C 4 resources in these hominin taxa. The earliest hominin species in the Turkana Basin, Australopithecus anamensis , derived nearly all of its diet from C 3 resources. Subsequently, by ca . 3.3 Ma, the later Kenyanthropus platyops had a very wide dietary range—from virtually a purely C 3 resource-based diet to one dominated by C 4 resources. By ca . 2 Ma, hominins in the Turkana Basin had split into two distinct groups: specimens attributable to the genus Homo provide evidence for a diet with a ca . 65/35 ratio of C 3 - to C 4 -based resources, whereas P. boisei had a higher fraction of C 4 -based diet ( ca . 25/75 ratio). Homo sp. increased the fraction of C 4 -based resources in the diet through ca . 1.5 Ma, whereas P. boisei maintained its high dependency on C 4 -derived resources.

Section: Evolution Of Hominin Diets Between 4 and 14 Ma In Eastern Amentioning

confidence: 98%

Stable isotope-based diet reconstructions of Turkana Basin hominins

Cerling

Manthi

Mbua

et al. 2013

189

178

“…afarensis do not differ significantly from the δ 13 C values of slightly younger Au. africanus from South Africa [median = −6.8‰, n = 24, Mann-Whitney U, P = 0.32 (2,(6)(7)(8)]. The ranges of variation in δ 13 C values for these two taxa broadly overlap (Au.…”

Section: Resultsmentioning

confidence: 99%

Diet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia

Wynn

Sponheimer

Kimbel

et al. 2013

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...

“…Although some Australopithecus species are younger than the time period reviewed here, they are all considered here for the purposes of this discussion. Species of Australopithecus generally have broad diets based on enamel carbon isotopic studies (63,87,91,104,107,108), with the exception of Au. anamensis (62) and the much younger Au.…”

Section: Pliocene Hominin Diversity Sympatry and The Question Of Nimentioning

confidence: 99%

The Pliocene hominin diversity conundrum: Do more fossils mean less clarity?

Haile‐Selassie

Melillo

2016

Recent discoveries of multiple middle Pliocene hominins have raised the possibility that early hominins were as speciose as later hominins. However, debates continue to arise around the validity of most of these new taxa, largely based on poor preservation of holotype specimens, small sample size, or the lack of evidence for ecological diversity. A closer look at the currently available fossil evidence from Ethiopia, Kenya, and Chad indicate that Australopithecus afarensis was not the only hominin species during the middle Pliocene, and that there were other species clearly distinguishable from it by their locomotor adaptation and diet. Although there is no doubt that the presence of multiple species during the middle Pliocene opens new windows into our evolutionary past, it also complicates our understanding of early hominin taxonomy and phylogenetic relationships.If one looks back over the controversies of human evolution, they have one element in common: new discoveries, theories, methods came along which no one in the controversy anticipated. The "facts" changed, and consequently people were not right or wrong in any simple way.S. L. Washburn and R. L. Ciochon, 1974 (1) New fossil discoveries and analytical methods that have proliferated during the last few decades have fundamentally changed how we study and interpret hominin fossils and understand human evolution. The discovery and subsequent naming of Australopithecus afarensis in the late 1970s was one of the major milestones in paleoanthropology (2). Its discovery not only pushed the record of hominins to earlier than 3 million years ago (Ma) (2), but also demonstrated the antiquity of human-like bipedality (3). However, the taxonomic homogeneity of the Au. afarensis hypodigm has been questioned since its naming (4-7), even though the Hadar fossil sample appears to be no more variable than other living ape species (8-11). A consensus emerged during the 1980s in which Au. afarensis, dated to between 3.7 and 2.9 Ma, was considered to be the sole early hominin species older than 3 Ma, largely supported by the lack of fossil evidence to indicate otherwise.When Australopithecus bahrelghazali was named in 1995 based on an approximately 3.5-Ma partial mandible from Chad (12), it was quickly dismissed as a geographic variant of Au. afarensis (13-15). The initial descriptions of Ardipithecus ramidus (16) and Australopithecus anamensis (17), followed by the naming of even earlier hominin species, such as Orrorin tugenensis (18), Ardipithecus kadabba (19,20), and Sahelanthropus tchadensis (21), extended the antiquity of our lineage as far back as >6 Ma. These early hominins initially appeared to show no temporal or spatial overlap, and hence reinforced the idea that the early phases of hominin evolution were characterized by phenetic continuity and phyletic gradualism, with only one hominin species existing in a region at any given time >3 Ma (e.g., ref. 22; see discussions below).The discovery of the Burtele partial foot from Ethiopia (23), the naming of Kenyan...