Anthropologists Reconstruct Diet of Early Human Ancestors

An international team of scientists has reconstructed dietary preferences of three groups of early hominins from the Cradle of Humankind, South Africa.

Reconstructions of Homo habilis, Australopithecus africanus and Paranthropus robustus (Edward Foster / John Gurche / Myartprints.com)

The study, published online in Nature, sheds more light on the diet and home ranges of early hominins belonging to three different genera – Australopithecus africanus, Paranthropus robustus and early Homo – that were discovered at sites such as Sterkfontein, Swartkrans and Kromdraai in the Cradle of Humankind, about 50 km from Johannesburg.

The anthropologists conducted an analysis of the fossil teeth, indicating that Australopithecus, a predecessor of early Homo, had a more varied diet than early Homo. Its diet was also more variable than the diet of another distant human relative Paranthropus.

“The results of the study show that Paranthropus had a primarily herbivorous-like diet, while Homo included a greater consumption of meat,” said co-author Prof Francis Thackeray, Director of the Institute for Human Evolution at Wits University.

Signatures of essential chemical elements have been found in trace amounts in the tooth enamel of the three fossils genera, and the results are indicators of what South African hominins ate and what their habitat preferences were.

Strontium and barium levels in organic tissues, including teeth, decrease in animals higher in the food chain. The scientists used a laser ablation device, which allowed them to sample very small quantities of fossil material for analysis.

Since the laser beam was pointed along the growth prisms of dental enamel, it was possible to reconstruct the dietary changes for each hominin individual.

“The greater consumption of meat in the diet of early forms of Homo could have contributed to the increase in brain size in this genus,” Prof Thackeray explained.

Australopithecus probably ate both meat and the leaves and fruits of woody plants. The composition of this diet may have varied seasonally.

Apart from the dietary differences, the new results indicate that the home-range area was of similar size for species of the three hominin genera.

The scientists also measured the strontium isotope composition of dental enamel. Strontium isotope compositions are free of dietary effects but are characteristic of the geological substrate on which the animals lived.

According to the study results, all the hominids lived in the same general area, not far from the caves where their bones and teeth are found today.

“Up until two millions years ago in South Africa, the Australopithecines were generalists, but gave up their broad niche to Paranthropus and Homo, both being more specialized than their common ancestor,” said lead author Prof Vincent Balter of the Geological Laboratory of Lyon in France.

Another study has recently reconstructed the diet of Australopithecus anamensis, a hominid that lived in the east of the African continent more than 4 million years ago.

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Bibliographic information: Balter et al. 2012. Evidence for dietary change but not landscape use in South African early hominins. Nature, published online 08 August 2012; doi: 10.1038/nature11349