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The discovery of Lucy in 1974 in Ethiopia marked the spirits because of the state of conservation of its skeleton and its age, 3.2 million years. Composed of 52 bone fragments, the study of Lucy's skeleton will reveal that she walked on both legs. This modern human ancestor of the species Australopithecus afarensis will become a world-wide celebrity who will not be clouded by later discoveries of other fossils.
Far in prehistory, the origins of man
Man is a primate of the genus Homo of the species sapiens whose pre-human ancestors, the australopithecines, constitute a branch resulting from a common trunk with the great apes of Africa. The first pre-human was discovered almost accidentally in southern Africa in 1924 by Raymond Dart, doctor and anatomist, who published his find in the journal Nature in 1925.
According to the most widespread theory of evolution, the human species was born more than 5 million years ago, during the Miocene era (25 million to 5 million years BC). . Earth's climate was much warmer and humid then than it is today, so tropical forest covered most of Africa, Europe and Asia. It was home to many species of primates, including our grandmother.
Towards the end of the Miocene, the temperature of the Earth cooled, the climate became drier, and ice caps formed at the poles. The forest withered away, giving way to vast expanses of woodland and grass. In East Africa, the first hominids (a family of primates including Homo sapiens and its immediate ancestors) saw their natural habitat shrink. Previously, they lived in trees and moved on their four limbs. In order to cross the great outdoors quickly and safely, some began to walk on two legs, thus inaugurating our mode of travel.
This development took place over several million years. The discovery of human fossils has enabled us to identify our most distant ancestors. The oldest known to this day; Ardepithecus ramidus, lived 4.4 million years ago, probably still in forests and on tree tops, like chimpanzees. It is not known if he was standing. Australopithecus afarensis, a more recent hominid, has been shown to be bipedal, since it appeared about 3.5 million years ago.
An international expedition
In 1972, an expedition of about thirty French, American and Ethiopian researchers set up. Research in southern and eastern Africa allowing the updating of Australopithecus remains being more and more fruitful, the paleontologist Yves Coppens, the geologist Maurice Taïeb and the American paleoanthropologist Donald Johanson, settled on the Hadar site, located in northwest Ethiopia, by the Awash River. It was at the end of long months of research that an assistant to Donald Johanson, Tom Gray, a student in paleontology, discovered on November 30, 1974, the skeleton of the one who would revolutionize our perception of human origins and, thereby , become a superstar.
Indeed, this new Australopithecus (Australopithecus afarensis), which emerged from the dawn of time, is exceptional in its state of preservation. With fifty-two bones, 40% of its skeleton is complete. As such, along with certain Australopithecus africanus from the Sterkfontein cave in South Africa, it became one of the most complete hominids of more than 3 million years ago.
This female skeleton, listed as AL 288, is named Lucy after the Beatles and their song Lucy in the Sky with Diamonds that the members of the expedition listen to in the evening by marking the discoveries of the day. This is followed by complex dating work which, thanks to the identification of a reliable volcanic marker located a little below the sediments which contained the fossil, reveals its age: 3.2 million years.
She is a female, about 20 years old, measuring just over a meter and weighing about 25 kg. Its cranial capacity is 400 cm3. Researchers suspect she drowned as indicated by her location and the nature of the sediment in which she was found. More recent hypothesis suggests she died falling from a tree
On the other hand, Lucy's detailed anatomical study shows that she still lived in trees much of her time, although on the ground, in the wooded savannah, she was bipedal. Its postcranial skeleton indeed presents a combination of characters which betray both a bipedal mode of locomotion - in view of the port of its head, the curvature of its spine, the shape of its pelvis and its femur - and a aptitude for arboreal life - as evidenced by his shoulder and elbow joints as well as his long arms and short legs.
It belongs to a species which evolved for several hundred thousand years in East Africa, from present-day Ethiopia to Tanzania, via Kenya. Lucy will be considered for many years to be the oldest species in human lineage. It will then be interpreted as a species related to the genus Homo.
Since Lucy's discovery, theOrrorin tugenensis, a 6 million year old fossil, has been unearthed in Kenya; in Ethiopia, researchers have also discovered theardipithecus kadabba 5.7 million years old. Finally, in 2001, the Sahelanthropus tchadensis, baptized "Tournaï" ("hope of life"), 7 million years old, was found in Chad. But he is the subject of considerable controversy due to his both human and simian characters. Man or gorilla? Researchers are divided. As for Lucy, she rests in the National Museum of Ethiopia, in Addis Ababa, the capital of the country.
- Le Rêve de Lucy, by Yves Coppens. Points, June 1997.
- The odyssey of the species, docu-fiction. DVD, France Tv, 2017.