Magazine article Science News

Getting a Grip on Prehistoric Tool Makers

Magazine article Science News

Getting a Grip on Prehistoric Tool Makers

Article excerpt

A small, unassuming bone runs halfway up the thumb from its base. That same bone offers scientists a surefire way to tell which ancient members of the human evolutionary family, known as hominids, possessed hands capable of making stone tools, according to a report in the Sept. 9 Science.

Moreover, an analysis of thumb fossils indicates that an extinct line of small-brained hominids called Paranthropus (or robust australopithecines) proved as anatomically prepared to fashion such implements as Homo erectus, a direct human ancestor, asserts Randall L. Susman, an anthropologist at the State University of New York at Stony Brook.

"I'm offering a new way to diagnose tool behavior," Susman says. "So far, it looks like no hominids were capable of tool making before 2.5 million years ago, and after that time all hominids were capable of tool making."

The new study supports Susman's prior elevation of Paranthropus to the status of tool maker, an assessment that challenged the widespread view that the Homo lineage held a monopoly on chipping useful devices out of stone (SN: 5/28/88, p.344).

The Stony Brook scientist examined lower-thumb bones of 12 pygmy chimpanzees, 49 common chimpanzees, and 41 modern humans, as well as single thumb fossils from Australopithecus afarensis (dating to about 3 million years ago), Paranthropus robustus (found at a 1.8-million-year-old South African cave), H. erectus (from the same cave), and a Neandertal dating to around 50,000 years ago.

Modern human specimens display a broad thumb head (where the joint forms) in relation to thumb length. …

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