Scientists Say Ancestors of Humans Walked on Their Knuckles

Scientists Say Ancestors of Humans Walked on Their Knuckles


Chronicle of Higher Education- March 23, 2000




The famed fossil Lucy harbors a most unladylike secret: In life, her wrists locked into place instead of bending backward, a sign that her ancestors -- and ours -- walked on their knuckles like modern chimpanzees and gorillas before striding only on their feet, report two paleoanthropologists at George Washington University.


The study "addresses one of the most fundamental questions that still remains in paleoanthropology today, and that is, 'Why did

humans first evolve?'" says Brian G. Richmond, a postdoctoral fellow, who described the findings in this week's issue of



Scientists have long debated how and why the primate ancestors of humans first came down from the trees. Some theories

have held that hominid species started walking upright immediately after they abandoned their arboreal way of life, perhaps

because of climatic drying that eliminated much of the African forests more than five million years ago.


The new evidence suggests that early hominids did not hit the ground running on two legs. Instead, they first moved overland by walking on their knuckles. Only later did they adopt an upright posture, suggest Mr. Richmond and his colleague David S.



The two found protrusions on the arm bones of Lucy, a specimen of Australophithecus afarensis, and the fossil of another

ancient species. The bumps are vestiges of the skeletal adaptations that allowed their ancestors to knuckle-walk. By the time of Lucy and her kin, about 2.5 million years ago, hominids had developed long legs and other adaptations that allowed them to

walk upright.


The new discovery will help sort out the evolutionary relationships among gorillas, chimpanzees, and human ancestors, write the anthropologists Mark Collard and Leslie C. Aiello, both of University College London, in a commentary on the article.