Early hominid's diet expands (Brief Article)

Australopithecus robustus, a hominid (member of the human evolutionary family) living in southern Africa about 1.8 million years ago, consumed a greater variety of foods than previously assumed, reports Andrew Sillen of the University of Cape Town, South Africa. Although some researchers claim these creatures mainly ate plants, nuts and seeds, analyses of two key minerals in A. robustus fossils suggest that their menu also included meat, Sillen contends.

A. robustus belongs to a line of hominid species -- placed within the genus Paranthropus by some investigators -- that died out about 1 million years ago. Fossils indicate that members of these species had relatively small brains and large jaws specialized for chewing. Several years ago, a study of A. robustus teeth found in a South African cave yielded microscopic evidence of nut and seed eating (SN: 7/2/88, p.14).

However, a low ratio of strontium to calcium in A. robustus fossils from the same cave reflects a diet that must have included animals as well as plants, Sillen asserts. He used a recently developed chemical technique to separate and measure the two substances in 50-milligram samples taken from nine. A. robustus skulls and jaws. Recent studies find low ratios of strontium to calcium among carnivores and substantially higher ratios among herbivores, Sillen says.

The South African researcher brands as "oversimplified" the widely accepted notion that A. robustus and its kin munched plants and seeds while direct human ancestors (belonging to the genus Homo) living in Africa at the same time ate an assortment of plant and animal foods. Research has begun on the mineral content of early Homo fossils also found in the South African cave. One sample from a Homo find shows a surprisingly high ratio of strontium to calcium. "It's a much higher ratio than we anticipated," Sillen remarks. "But it's only one specimen, and we're not sure what it means at this point."