Ardi Is a New Piece for the Evolution Puzzle
Figuring out the story of human origins is like assembling a huge, complicated jigsaw puzzle that has lost most of its pieces. Many will never be found, and those that do turn up are sometimes hard to place. Every so often, though, fossil hunters stumble upon a discovery that fills in a big chunk of the puzzle all at once — and simultaneously reshapes the very picture they thought they were building.
The path of just such a discovery began in November 1994 with the unearthing of two pieces of bone from the palm of a hominid hand in the dusty Middle Awash region of Ethiopia. Within weeks, more than 100 additional bone fragments were found during an intensive search-and-reconstruction effort that would go on for the next 15 years and culminate in a key piece of evolutionary evidence revealed this week: the 4.4 million–year–old skeleton of a likely human ancestor known as Ardipithecus ramidus (abbreviated Ar. ramidus)...
... So what does that mean? Based on Ardi's anatomy, it appears that chimpanzees may actually have evolved more than humans — in the scientific sense of having changed more over the past 7 million years or so. That's not to say Ardi was more human-like than chimplike. White describes her as an "interesting mosaic" with certain uniquely human characteristics: bipedalism, for one. Ardi stood 47 in. (120 cm) tall and weighed about 110 lb. (50 kg), making her roughly twice as heavy as Lucy. The structure of Ardi's upper pelvis, leg bones and feet indicates she walked upright on the ground, while still retaining the ability to climb. Her foot had an opposable big toe for grasping tree limbs but lacked the flexibility that apes use to grab and scale tree trunks and vines ("Gorilla and chimp feet are almost like hands," says Lovejoy), nor did it have the arch that allowed Australopithecus and Homo to walk without lurching side to side. Ardi had a dexterous hand, more maneuverable than a chimp's, that made her better at catching things on the ground and carrying things while walking on two legs. Her wrist, hand and shoulder bones show that she wasn't a knuckle walker and didn't spend much time hanging or swinging ape-style in trees. Rather, she moved along branches using a primitive method of palm-walking typical of extinct apes. "[Ardi is] a lovely Darwinian creature," says Penn State paleoanthropologist Alan Walker, who was not involved in the discovery. "It has features that are intermediate between the last common ancestor and australopithecines."
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The path of just such a discovery began in November 1994 with the unearthing of two pieces of bone from the palm of a hominid hand in the dusty Middle Awash region of Ethiopia. Within weeks, more than 100 additional bone fragments were found during an intensive search-and-reconstruction effort that would go on for the next 15 years and culminate in a key piece of evolutionary evidence revealed this week: the 4.4 million–year–old skeleton of a likely human ancestor known as Ardipithecus ramidus (abbreviated Ar. ramidus)...
... So what does that mean? Based on Ardi's anatomy, it appears that chimpanzees may actually have evolved more than humans — in the scientific sense of having changed more over the past 7 million years or so. That's not to say Ardi was more human-like than chimplike. White describes her as an "interesting mosaic" with certain uniquely human characteristics: bipedalism, for one. Ardi stood 47 in. (120 cm) tall and weighed about 110 lb. (50 kg), making her roughly twice as heavy as Lucy. The structure of Ardi's upper pelvis, leg bones and feet indicates she walked upright on the ground, while still retaining the ability to climb. Her foot had an opposable big toe for grasping tree limbs but lacked the flexibility that apes use to grab and scale tree trunks and vines ("Gorilla and chimp feet are almost like hands," says Lovejoy), nor did it have the arch that allowed Australopithecus and Homo to walk without lurching side to side. Ardi had a dexterous hand, more maneuverable than a chimp's, that made her better at catching things on the ground and carrying things while walking on two legs. Her wrist, hand and shoulder bones show that she wasn't a knuckle walker and didn't spend much time hanging or swinging ape-style in trees. Rather, she moved along branches using a primitive method of palm-walking typical of extinct apes. "[Ardi is] a lovely Darwinian creature," says Penn State paleoanthropologist Alan Walker, who was not involved in the discovery. "It has features that are intermediate between the last common ancestor and australopithecines."