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Alan Alda in Scientific American Frontiers








 
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photo of skullIn"Handmade Humans ," Dr. William Kimbel, a physical anthropologist at the Institute of Human Origins and Arizona State University, introduced us to Lucy, perhaps the most famous fossil of all time. Lucy's discovery revolutionized our understanding of human evolution. Anthropologists had long thought that intelligence predated bipedalism, the ability to walk upright. With her chimp-like brain capacity, but human-like pelvis and knee, Lucy provides strong evidence that bipedalism came first, as far back as 3.2 million years ago. According to some scientists, this upright posture freed up Lucy's descendants' hands for tool making and weapon use. These tasks in turn created the need for an increasingly complex brain, leading these upright apes down the evolutionary path that would lead to modern human beings.
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How Lucy Came to Light

On November 30th, 1974, researcher Donald Johanson was surveying for fossils of human ancestors near the Awash River in Hadar, Ethiopia. Glancing over his shoulder as he headed back to his Land Rover, Johanson noticed several bone fragments poking out of the ground- a bit of skull, a jaw bone, a leg. Johanson would eventually unearth about 40 percent of the skeleton we now know as Lucy, the oldest and most complete remains of a human ancestor. The skeleton earned her memorable moniker when the Beatles's song "Lucy in the Sky with Diamonds" played over and over at the festivities later that night.

photo of Don Johanson
Don Johanson fossil hunting in Hadar, Ethiopia where 13 A. Afarensis skeletons were found  

Lucy belonged to a species Johanson and his colleagues dubbed Australopithecus afarensis -literally "southern ape from East Africa" -one of the earliest species of hominids, the family of bipedal primates which includes Homo habilis ("handy man") and Homo erectus ("upright man"). She stood only three and half feet tall and probably weighed 60 to 65 pounds. Her small stature suggests she was female, since male australopithecines could reach heights up to five feet. Evidence from the molars, joints and spine indicate Lucy was a young adult, maybe 21 years of age when she died. Her bones reveal little about her demise, but since they were found intact and not scattered by predators, scientists believe she died of natural causes. Her corpse likely sunk into the soft sediments on the banks of the Awash, where she remained undisturbed for more than 3 million years.

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Photos:Gerald Heine, Dept. of Anthropology, Cal State U. Sacramento; Institute of Human Origins

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