SCIENCE

Teeth Tales

Fossils tell a new story about the diversity of hominid diets

Eric Jaffe
Paranthropus robustus
Anthropologists recently found fossils of Paranthropus robustus, also called robust australopithecines, in an excavation site in South Africa. Paranthropus coexisted with human ancestors Homo habilis and Homo erectus as recently as 1.5 million years ago. Some anthropologists had believed that Paranthropus' limited diet caused its extinction, but new evidence from the fossils suggests that Paranthropus had a varied diet that included both hard and soft plants as well as herbivores. Courtesy of Science

About two million years ago, early human ancestors lived alongside a related species called Paranthropus in the African savanna. Members of Paranthropus had large molars and strong jaw muscles, and some scientists have assumed that the species ate hard, low-nutrient shrubs and little else.

Anthropologists often consider that limited diet the reason Paranthropus died out one million years ago, whereas early humans, with their more flexible eating habits, survived.

But a new study of Paranthropus fossils suggests a different story. A team of scientists led by Matt Sponheimer of the University of Colorado at Boulder recently analyzed four 1.8-million-year-old Paranthropus teeth found at the Swartkrans Cave — a well-known archeological site in South Africa.

After studying each tooth's enamel with a new technique called laser ablation, Sponheimer's team concludes in the Nov. 10 Science that Paranthropus had a surprisingly varied diet. Far from confined to eating shrubs, trees and bushes, Paranthropus likely had a rich diet that included grass, sedges and herbivores. This diet apparently changed from season to season and even year to year, perhaps enabling Paranthropus to adapt to prolonged droughts.

The success of laser ablation — a far less invasive technique than traditional drilling — should persuade museum curators to allow scientists greater access to teeth fossils, argues anthropologist Stanley Ambrose of the University of Illinois at Urbana-Champaign in a commentary accompanying the research paper.

For now, the results give Sponheimer's team a new thought to chew on: some unknown, non-dietary difference must explain the diverging fates of Paranthropus and Homo.

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Anthropologists recently found fossils of Paranthropus robustus, also called robust australopithecines, in an excavation site in South Africa. Paranthropus coexisted with human ancestors Homo habilis and Homo erectus as recently as 1.5 million years ago. Some anthropologists had believed that Paranthropus' limited diet caused its extinction, but new evidence from the fossils suggests that Paranthropus had a varied diet that included both hard and soft plants as well as herbivores. Courtesy of Science
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A research team led by Matt Sponheimer analyzed Paranthropus teeth using a technique called laser ablation. The new, fossil-safe method allowed Sponheimer's team to detect various carbon isotopes typically left on tooth enamel by different types of plants. "They are literally blazing a new trail to answers to fundamental questions" about hominid evolution, writes anthropologist Stanley Ambrose about the new research. Courtesy of Science
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Anthropologists discovered the Paranthropus teeth fossils in Swartkrans Cave in South Africa. The site has been a boon to archaeologists; it contains bone-digging sticks and other tools used by early hominids, as well as early records of fire. Courtesy of Science

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Eric Jaffe

Eric Jaffe is a contributing writer to The Atlantic Cities and the author of the book The King's Best Highway: The Lost History of the Boston Post Road, the Route That Made America.