doFifty years after her discovery in Ethiopia on November 24, 1974, Lucy remains an icon among prehuman fossils. When the American Donald Johanson and Tom Gray, the student who accompanied him, saw some bone fragments protruding from an arid hill in Afar, they quickly understood that they had in their hands the holy grail of every paleoanthropologist. A specimen would quickly appear that represents 40% of the skeleton of the same individual, something unprecedented in such an ancient period: around 3.2 million years.
The same year, in Tanzania, a lower jaw was unearthed, which will be associated with the same species. In 1975, 200 fossils were in turn exhumed in Afar, representing seventeen probably related individuals. Others will follow, including the fossil of a three-year-old boy found in Dikika (Ethiopia) in 2000. Called Selam, he will be mistakenly described as “Lucy’s son”: he would have been born about 100,000 years before her.
This abundance of fossils led, in 1978, the Americans Donald Johanson and Tim White and the Frenchman Yves Coppens (1934-2022), co-director of the Afar expedition, to propose a species name for Lucy and her ilk: Australopithecus afarensiswhose dates cover a period ranging from approximately 3.8 million to 3 million years ago, making him the oldest potential human ancestor.
Fifty years later, what is the status of this australopithecus (1.10 m tall and less than 30 kilograms) in our phylogenetic tree? For Donald Johnson, A. afarensis “it remains our most probable ancestor and constitutes one of the most important species in the history of human evolution”. Thus concludes an article co-authored with his Ethiopian colleague Yohannes Haile-Selassie, in ScientistAmerican of November (and in its French version, for science), on the occasion of the anniversary of the discovery.
“Our great aunt”
The two researchers also review the many new species in the human lineage since its split from that of chimpanzees, which we call hominids, discovered over the past half century.
First are the oldest, Sahelanthropus tchadensis (Chad), alias Toumaï, and Orrorin tugenensis (Kenya), 7 and 6 million years old respectively, and already bipedal. But also anamensissometimes presented as a close ancestor of Lucy, of which it was recently learned that the two species had probably coexisted. And all his contemporaries, increasingly numerous (A. bahrelghazalialias Abel, and A. deyiremeda, or even Kenyanthropus platyops).
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