Lucy (Australopithecus)

Lucy (also given a second (Amharic) name: ድንቅነሽ dinqineš, "you are wonderful" ) is the common name of AL 288-1, the 40% 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.

Discovery
French geologist Maurice Taieb discovered the Hadar Formation in 1972. He then formed the IARE, inviting Donald Johanson, an American anthropologist now head of the Institute of Human Origins of Arizona State University, and Yves Coppens, a French born paleontologist now based at the Collège de France to co-direct the research. An expedition was formed with four American and seven French participants, and in the autumn of 1973 the team surveyed Hadar, Ethiopia 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, which had been sliced slightly on the front. The lower end of a thighbone was found near to it, and when he fitted them together the angle of the knee joint clearly showed that this fossil, reference AL 129-1, was an upright walking hominid. Over three million years old, the fossil was much older than any others known at the time. The site lay about two and a half kilometres from the site at which they subsequently found "Lucy".

The team returned for the second field season in the following year and found hominid jaws. Then, on the morning of November 30, 1974, near the Awash River, Johanson, abandoning a plan to update his field notes, joined one of his students, Tom Gray, in a search for bone fossils at Locality 162.

Both Johanson and Gray spent a couple of hours on the increasingly hot arid plains, surveying the dusty terrain, and were about to head back to camp 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, they found more and more bones, including part of a thighbone, vertebrae, part of a pelvis indicating that the fossil was female, ribs, and pieces of jaw. They marked the spot and returned to camp, excited at finding so many pieces apparently from one individual.

In the afternoon, everyone on the expedition was at the gully, sectioning off the site and preparing for careful collection which eventually took three weeks. That first evening they celebrated at the camp, staying up all night, and at some stage during the evening the fossil AL 288-1 was nicknamed Lucy, after the Beatles song "Lucy in the Sky with Diamonds", which was being played loudly and repeatedly on a tape recorder in the camp.

Over the three weeks, several hundred pieces or fragments of bone were found, with no duplication, confirming their original speculation that they were from the one skeleton. As the team analyzed the fossil further, they calculated that an amazing 40% of a hominin skeleton had been recovered, an astounding accomplishment in the world of anthropology. Usually, only fossil fragments are discovered; rarely are skulls or ribs found intact. Johanson considered it was female based on the one complete pelvic bone and sacrum indicating the width of the pelvic opening. 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 hominins had walked erect.

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/human common ancestor 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 an agreement with the government of Ethiopia, and returned it according to agreement some 9 years later. Lucy as a fossil hominin significantly captured public notice, becoming almost a household name at the time.

Currently, the prevailing opinion is that the Lucy skeleton should be classified in the species Australopithecus afarensis. Lucy is preserved at the National Museum of Ethiopia 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. 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 displayed 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 1970s giving anthropologists a much better appreciation of the range of variability and sexual dimorphism of the species.

Postcranial
One of the most striking characteristics possessed by Lucy was a valgus knee, which indicated that she normally moved by walking upright. Her femoral head was small and her femoral neck was short, both primitive characteristics. Her greater trochanter, however, was clearly derived, being short and human like 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.

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.

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.

US tour
A six-year exhibition tour of the United States titled Lucy’s Legacy: The Hidden Treasures of Ethiopa features the Lucy fossil as well as over 100 artifacts from ancient times to the present. The tour was approved by the Ethiopian government and organized in collaboration with the Houston Museum of Natural Science, where it will be on display from August 31, 2007 to April 20, 2008. An undisclosed proportion of the proceeds from the tour is to go toward modernizing Ethiopia's museums. The U.S. Department of State also approved the tour. There was controversy in advance of the tour over concerns about the fragility of the specimens, with various experts including paleoanthropologist Owen Lovejoy and anthroplogist and conservationist Richard Leakey publicly stating their opposition. The Smithsonian Institution was amongst museums declining to host the exhibits. The fossil's discoverer Don Johanson stated that although he was somewhat uneasy about the possibility of damage, he did not oppose exhibiting Lucy as it will help to raise awareness of human-origins studies. The museum is making arrangements for the exhibits to be shown at as many as ten other museums.