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Researchers get their teeth into hominins' diet
14 August 2012
CNRS (Délégation Paris Michel-Ange)
What did our early ancestors the hominins eat? Fossil teeth discovered in South Africa suggest that the Australopithecus, Paranthropus and Homo genera (1), who lived in that region about two million years ago, adopted very different dietary habits. This is the conclusion reached by researchers from the Laboratoire de Géologie de Lyon (CNRS / ENS Lyon / Université Claude Bernard Lyon 1) and the Laboratoire d’Anthropologie Moléculaire et Imagerie de Synthèse (CNRS / Université Toulouse III - Paul Sabatier / Université de Strasbourg). Their findings, published in the August 8, 2012 issue of Nature, will shed light on certain biological and social aspects of human evolution.
Since the late 1930s, hominin fossils have been unearthed regularly in South Africa, a region where the Australopithecus genus thrived, succeeded by Paranthropus and Homo. However, all of these remains have come from the same archaeological deposits. Now a team of geochemists and biologists has successfully reconstructed the dietary habits of these three hominin genera.
The researchers focused on the strontium and barium content in the tooth enamel of several fossils from these populations. The higher a mammal’s rank in the food chain, the smaller the concentration of these two elements in its biological tissues, including this part of the teeth. The originality of the present study lies in the researchers’ use of the laser ablation technique to take these measurements. The laser beam was directed along the growth prisms of dental enamel, making it possible to reconstruct each individual’s dietary changes over a period of their life. The results show that the australopithecines had a much more varied diet than the other two hominin genera. Paranthropus was consistently herbivorous, as was already inferred from their facial and dental anatomy, while Homo was more carnivorous.
The team also measured the isotopic composition of the strontium contained in the samples, a distinctive characteristic of the geological substrate on which es fed. Here again, there is no room for doubt: all of the hominins studied lived in the same region, near the caves where their fossilized remains are found today.
In light of these results, some pieces of the ecological puzzle fall into place. About 2 million years ago, the “opportunistic” australopithecines (who ate whatever they could find: animal carcasses, berries, etc.) were succeeded by Paranthropus and Homo, each of which was more “specialized” than their common ancestor. Paranthropus fed exclusively on plants, which could be very tough and woody (roots, bulbs), while Homo, probably with the help of stone tools, mostly relied on hunting for food. These two species cohabited for nearly a million years before the former disappeared for reasons unknown.
This research was funded by CNRS and the French Ministry of Foreign Affairs.
(1) Australopithecus, Paranthropus and Homo are three hominin genera. The Australopithecus genus first appeared about 4 million years ago and has been extinct for 2 million years. Paranthropus, also extinct, lived in Africa between approximately 2.5 and 1.2 million years ago. Homo, which first appeared about 2.3 to 2.4 million years ago, is the genus that comprises modern man and related species. All species of the Homo genus are now extinct except Homo sapiens.
Upper right first molar of an Early Homo. Photo: José Braga and Didier Descouens.
Upper right third molar of a Paranthropus robustus. Photo: José Braga and Didier Descouens.
Lower right first molar of an Early Homo. Photo: José Braga and Didier Descouens.