Diet and the evolution of the earliest human ancestors

Abstract

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. Since the discovery of Australopithecus afarensis, many researchers have emphasized the importance of bipedality in scenarios of human origins (1,2). Surprisingly, less attention has been focused on the role played by diet in the ecology and evolution of the early hominids (as usually received). Recent work in a broad range of disciplines, such as paleoenvironmental studies (3, 4), behavioral ecology (5), primatology (6), and isotope analyses (7), has rekindled interests in early hominid diets. Moreover, important new fossils from the early Pliocene raise major questions about the role of dietary changes in the origins and early evolution of the Hominidae (8-10). In short, we need to focus not just on how the earliest hominids moved between food patches, but also on what they ate when they got there.This paper presents a review of the fossil evidence for the diets of the Pliocene hominids Ardipithecus ramidus, Australopithecus anamensis, Australopithecus afarensis, and Australopithecus africanus. These hominids offer evidence for the first half of human evolution, from our split with prehistoric apes to the earliest members of our own genus, Homo. The taxa considered are viewed as a roughly linear sequence from Ardipithecus to A. africanus, spanning the time from 4.4 million to 2.5 million years ago. As such, they give us a unique opportunity to examine changes in dietary adaptations of our ancestors over nearly 2 million years. We also trace what has been inferred concerning the diets of the Miocene hominoids to put changes in Pliocene hominid diets into a broader temporal perspective. From such a perspective, it becomes clear that the dietary capabilities of the early hominids changed dramatically in the time period between 4.4 million and 2.3 million years ago. Most of the evidence has come from five sources: analyses of tooth size, tooth shape, enamel structure, dental microwear, and jaw biomechanics. Taken together, they suggest a dietary shift in the early australopithecines, to increased dietary flexibility in the face of climatic variability. Moreover, changes in diet-related adaptations from A. anamensis to A. afarensis to A. africanus suggest that hard, abrasive foods became increasingly important through the Pliocene, perhaps as critical items in the diet. Tooth SizeIn 1970, Jolly (11) noted that australopithec...

Early hominin diet included diverse terrestrial and aquatic animals 1.95 Ma in East Turkana, Kenya

“…Geochemical compo- This article is a PNAS Direct Submission. 1 To whom correspondence should be addressed. E-mail: david.braun@uct.ac.za.…”

“…Oldowan | Paleolithic | stone tools | paleomagnetism S tone artifact production has long been considered a hallmark of human behavior and is often associated with brain expansion and changing patterns of hominin diet (1). The incorporation of animal tissue into the diet of late Pliocene (we refer here to previous definitions of the Pliocene to be consistent with previous descriptions of the paleoanthropological record) hominins is widely considered to be key to the suite of adaptations (e.g., enlarged brain, tooth size reduction, smaller gut, and increased body size) that began to set the earliest members of our genus apart from their ancestors and relatives.…”

The Energetics of Encephalization in Early Hominids

“…Various lines of evidence (e.g., comparative primate studies, stable isotopes, dental microwear, etc.) suggest that australopithecines consumed a varied and opportunistic diet that was largely composed of plant foods, such as fruits, seeds, and leaves, and included an assortment of C 4 foods (e.g., grasses, sedges, and termites) (Teaford and Ungar, 2000;Sponheimer et al, 2005). Important dietary differences almost certainly existed between species, with certain later australopithecines (e.g., Australopithecus africanus) apparently expanding their dietary flexibility and breadth, and robust australopithecines (e.g., A.…”

Quantitative analysis of dental microwear in hadrosaurid dinosaurs, and the implications for hypotheses of jaw mechanics and feeding

“…Microwear refers to the microscopic polished, scratched, or pitted textures produced in vivo by the actions of abrasives in food and by the compressive and shearing forces that act on teeth during feeding (13,14). Quantitative analysis of tooth microwear is an extremely powerful tool and has been applied extensively to fossil primates and hominins to evaluate the role of dietary changes in human evolution (15,16). Applied to extinct nonprimate mammals, quantitative tooth microwear analysis has also provided direct evidence of tooth use, diet, and feeding (13,17,18) and has revealed how feeding in ungulates has tracked past environmental change (19).…”