Half a century ago, a discovery in Ethiopia rewrote the chapters of human evolution. Until then, it was believed that our ancestors evolved linearly: they became taller, had larger brains and learned to walk on two legs, culminating in Homo sapiens. This simplistic view was popularized by images such as the “March of Progress”, which showed a continuous evolution from apes to modern humans. However, on November 24, 1974, a 3.2 million-year-old skeleton appeared to challenge this concept, named Lucy.
Part of Lucy's reconstructed skeleton, on display at the Cleveland Museum of Natural History in 2006. Credit: James St. John /CC BY 2.0 The research led by paleoanthropologist Donald Johanson was described in a 1978 paper, in details that changed our understanding . of how we become human.
The knee that changed everything When Johanson found Lucy's bones, they initially looked normal. However, the shape of the knee was surprising, indicating that Lucy walked upright, like modern humans. Until then, it was believed that bipedalism only evolved with larger brains.
“This showed beyond any doubt that she was walking upright. It was a turning point for our understanding of human evolution,” Johanson told German website DW. According to him, the fact that Lucy had a small brain, similar to that of a chimpanzee, refuted the idea that walking upright and increased intelligence arose at the same time.
“Lucy reinforced the argument that our ancestors learned to walk before they developed large brains and more advanced cognitive abilities,” said the paleoanthropologist.
Reconstruction of the appearance and skeleton of Lucy, a prehistoric woman who lived 3.2 million years ago. Credit: Cleveland Museum of Natural History Read more:
Relatives of the fossil Lucy used tools 3.2 million years ago The path of human evolution is revealed by a 150,000-year-old shelter The “Stone Monkey Theory” claims that the human brain evolved from drug-using primates Human evolution is like a tree or a river Lucy's discovery also challenged the idea that human evolution was a straight line. Today, scientists compare this process to a “fat tree,” with many branches representing different species. Some of these branches grew and evolved, while others were eliminated by extinction.
An alternative metaphor, proposed by paleoanthropologist Andy Herries, is that of a “braided river” in which the first human populations mixed, evolved or disappeared. This approach explains phenomena such as the interbreeding between Homo sapiens and Neanderthals and the extinction of species such as Homo floresiensis, which inhabited Indonesia until around 50,000 years ago.
Donald Johanson, responsible for Lucy's discovery, named after the 1967 Beatles song “Lucy in the Sky with Diamonds”, which was played loudly at the expedition camp. Credit: Institute of Human Origins/Arizona State University About Lucy, the world's most famous fossil:
The species was classified as Australopithecus afarensis, named after the Afar people of the region where it was found; Although it is probably not our direct ancestor, its discovery was crucial in revealing the complexity of human evolution; Lucy's legacy also helped identify other early species that coexisted around three million years ago. Despite the gaps that still exist in history, each new fossil found expands our knowledge of how we became Homo sapiens. For Johanson, Lucy is a symbol of this search. “It has become a mascot of evolution, helping to build a richer, more detailed picture of our origins.”