August 9, 2012
Our Early Human Ancestors – Hominins – Had Varying Diet Preferences
April Flowers for redOrbit.com - Your Universe Online
An international team of scientists has reconstructed the dietary preferences of 3 groups of hominins found in South Africa.
The paper, “Evidence for diet but not landscape use in South African early hominins," is a joint effort between the Ecole Normale SupÃ©rieure, the UniversitÃ© de Toulouse Paul Sabatier, and the University of the Witwatersrand and has been selected for Advanced Online Publication in the journal Nature.
The research sheds more light on the diet and home ranges of the early hominins belonging to three different genera, notably Australopithecus, Paranthropus and Homo, that were discovered at sites such as Sterkfontein, Swartkrans, and Kromdraai in the Cradle of Humankind. The Cradle of Humankind, about 50 kilometers northwest of Johannesburg, South Africa, has produced a large number of hominid fossils, as well as some of the oldest ever found.
Hominin is a fairly new designation, a bit more specific than the older term Hominid. Hominids now include all modern and extinct Great Apes (that is modern humans, chimpanzees, gorillas, and orangutans and all their immediate ancestors), while the newer term hominin consists of modern humans, extinct human species, and all our immediate ancestors (including members of the genera Homo, Australopithecus, Paranthropus and Ardipithecus).
The scientists conducted an analysis of the fossil teeth. Signature elements of 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.
Results of the study indicated that Australopithecus (a predecessor of early Homo who existed before the other two genera evolved about 2 million years ago), had a more varied diet than early Homo. Its diet was almost more variable than that of another distant human relative known as Paranthropus.
According to the team, Parathropus had a primarily herbivorous-like diet, while Homo included a greater consumption of meat. Australopithecus probably ate both meat and the leaves and fruits of woody plants. The composition of this diet may have varied seasonally. Francis Thackery, Director of the Institute for Human Evolution at Wits University states that 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.
Though their dietary habits differed, the results of the study show that all three groups had similar-sized home ranges.
The scientists have 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 results all the hominids lived in the same general area, not far from the caves where their bones and teeth are found today.
Professor Vincent Balter of the Geological Laboratory of Lyon in France, suggests that 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.