Lucy (Australopithecus)

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Catalog number:	AL 288-1
Common name:	Lucy
Species:	Australopithecus afarensis
Age:	3.2 mya
Place discovered:	Afar Depression, Ethiopia
Date discovered:	1974
Discovered by:	Donald Johanson

Lucy (Amharic ድንቅነሽ dinqneš, "you are wonderful") is the common name of AL 288-1, the remarkably near complete Australopithecus afarensis skeleton discovered on November 30, 1974 by the International Afar Research Expedition (IARE; director: Maurice Taieb, co-directors: Donald Johanson and Yves Coppens) in the Awash Valley of Ethiopia's Afar Depression. Lucy is estimated to have lived 3.2 million years ago.

1 Discovery
2 Notable characteristics
3 See also
4 References
5 External links

[edit] Discovery

French geologist Maurice Taieb discovered the Hadar Formation in 1972. He then formed the IARE, inviting notably Johanson, an American anthropologist now head of the Institute of Human Origins of Arizona State University, and Coppens, a French born paleontologist now based at the Collège de France to co-direct the research. The team surveyed Hadar, Ethiopia during the 1970s for fossils and artifacts related to the origin of humans. In November 1973, near the end of the first field season, Johanson noticed a fossil of the upper end of a shinbone. The lower end of a thighbone was found next to it, and when he fitted them together the knee joint clearly showed that this was an upright walking hominid (after comparison with modern bones that Johanson found in a recent Afar grave).^[1]^[2]

They returned for the second field season in the following year and found hominid jaws. Then, on November 30, 1974, near the Awash River, Johanson abandoned a plan to update his field notes to join one of his students, Tom Gray, searching for bone fossils. Both were on the hot arid plains surveying the dusty terrain when a fossil caught Gray's eye; an arm bone fragment on a slope in a gulley. Near it lay a fragment from the back of a small skull. As they looked further, more and more bones were found, including jaw, arm bone, thighbone, ribs, and vertebrae. Both Johanson and Gray carefully analyzed the partial skeleton and calculated that an amazing 40% of a hominin skeleton was recovered, which, while sounding generally unimpressive, is astounding in the world of anthropology. Usually, only fossil fragments are discovered; rarely are skulls or ribs found intact. As the team analyzed the fossil further, Johanson argued it was female based on the feminine stature of the skeleton. The skeleton AL 288-1 was nicknamed Lucy, after the Beatles song "Lucy in the Sky with Diamonds", which was played repeatedly on a tape recorder at the camp as they celebrated all night after finding the first bones. Lucy was only 1.1 m (3 feet 8 inches) tall, weighed 29 kilograms (65 lb) and looked somewhat like a Common Chimpanzee, but although the creature had a small brain, the pelvis and leg bones were almost identical in function with those of modern humans, showing with certainty that these hominids had walked erect.^[3]

Johanson and his colleague Tim White, a Californian born paleoanthropologist, placed Australopithecus afarensis as the last ancestor common to humans and chimpanzees living from 3.9 to 3 million years ago. Although fossils closer to the chimpanzee line have been recovered since the early 1970s, Lucy remains a treasure among anthropologists studying Human origins. The fragmentary nature of the older fossils furthermore deter confident conclusions as to the degree of bipedality or their relation to true hominines.

Johanson brought the skeleton back to Cleveland, under agreement with the government of the time in Ethiopia, and returned it according to agreement some 9 years later. Lucy was the first fossil hominin to really capture public notice, becoming almost a household name at the time. Current opinion is that the Lucy skeleton should be classified in the species Australopithecus afarensis. Lucy is preserved at the national Museum in Addis Ababa, Ethiopia. A plaster replica is displayed instead of the original skeleton. A cast of the original skeleton in its reconstructed form remains on display at the Cleveland Museum of Natural History^[4]. A diorama of Australopithecus afarensis and other human predecessors showing each species in its habitat and demonstrating the behaviors and capabilities that scientists believe it had is in the Hall of Human Biology and Evolution at the American Museum of Natural History in New York City.

Further discoveries of afarensis specimens occurred during the 1970's giving anthropologists a much better appreciation of the range of variability and sexual dimorphism of the species.

[edit] Notable characteristics

[edit] Postcranial

One of the most striking characteristics possessed by Lucy was a valgus knee, which indicated that she normally moved by means of upright walking. Her femoral head was small and her femoral neck was short, both primitive characteristics. Her greater trochanter, however, was clearly derived, being short and humanlike rather than taller than the femoral head. The length ratio of her humerus to femur was 84.6% compared to 71.8% for modern humans and 97.8% for common chimpanzees, indicating that either the arms of A. afarensis were beginning to shorten, the legs were beginning to lengthen, or that both were occurring simultaneously. Lucy also possessed a lumbar curve, another indicator of habitual bipedalism.

[edit] Pelvic girdle

Johanson was able to recover Lucy's left innominate bone and sacrum. Though the sacrum was remarkably well preserved, the innominate was distorted, leading to two different reconstructions. The first reconstruction had little iliac flare and virtually no anterior wrap, creating an ilium that greatly resembled that of an ape. However, this reconstruction proved to be faulty, as the superior pubic rami would not have been able to connect if the right ilium was identical to the left. A later reconstruction by Tim White showed a broad iliac flare and a definite anterior wrap, indicating that Lucy had an unusually broad inner acetabular distance and unusually long superior pubic rami. Her pubic arch was over 90 degrees, similar to modern human females. Her acetabulum, however, was small and primitive, like that of a chimpanzee.

[edit] Cranial specimens

The cranial evidence recovered from Lucy are far less derived than her postcranium. Her neurocranium is small and primitive, while she possesses more spatulate canines than apes.

This was due to the earlier belief (1950-1970's) that increasing brain size of apes was the trigger for evolving towards humans. Before Lucy, a fossil called '1470' (Homo rudolfensis) with a brain capacity of about 800 cubic centimetres had been discovered, an ape with a bigger brain. If the older theory was correct, humans most likely evolved from the latter. However, it turned out Lucy was the older fossil, yet Lucy was bipedal (walked upright) and had a brain of only around 375 to 500 cc. These facts provided a basis to challenge the older views.