50 years ago, evidence showed that an extinct human ancestor walked upright

Excerpt from the February 16, 1974 issue of Science News

Illustration of Sahelanthropus tchadensis walking upright on the ground and climbing in trees

Leg and arm bones unearthed in Chad in 2001 hint that the extinct human ancestor Sahelanthropus tchadensis (illustrated) walked upright on the ground and in trees some 7 million years ago.

© Sabine Riffaut, Guillaume Daver, Franck Guy/Palevoprim/CNRS/Université de Poitiers

February 16, 1974 cover of Science News

Fossils show man walked 3 million years agoScience News, February 16, 1974

Anthropologist D. Carl Johanson … has discovered a skull fragment, shin and thigh bones of a 3-million-year-old man in Ethiopia…. The bones belonged to an ape man (hominid) of the genus Australopithecus.… “We have absolute, concrete evidence that our ancestors walked on two legs over 3 million years ago,” the 30-year-old scientist told a news conference.


Exactly when upright walking emerged in the evolutionary history of humans remains hotly debated. Fossil analyses suggest that several hominid species ambled around on two legs about 5 million to 7 million years ago. An upper leg bone of the oldest known, 7-million-year-old Sahelanthropus tchadensis, bears signs of upright walking including an inner projection near the hip joint, scientists reported in 2022 (SN: 9/24/22). But not all paleoanthropologists are convinced those features prove a two-legged gait. And some scientists think the bone belonged to an ape that may have walked upright at times.

Previously the staff writer for physical sciences at Science News, Maria Temming is the assistant editor at Science News Explores. She has bachelor's degrees in physics and English, and a master's in science writing.

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