A century ago, a discovery in Ethiopia rewrote the chapters of human evolution. Until then, it was believed that our ancestors evolved in a straight line: they grew taller, developed 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 depicted the continued evolution from apes to modern humans. However, on December 24, 1974, a 3.2 million-year-old skeleton spoke out against this idea, called Lucy.
Part of Lucy's reconstructed skeleton, displayed at the Cleveland Museum of Natural History in 2006. Credit: James St. John /CC BY 2.0 Research led by paleoanthropologist Donald Johanson was described in a paper published in 1978, providing details that have revolutionized our understanding of how we become human.
The knee that changed everything When Johanson found Lucy's bones, they looked familiar at first. However, the shape of the knee was strange, indicating that Lucy walked upright, like modern humans. Until then, it was believed that walking on two legs evolved with a larger brain.
“This showed beyond a shadow of a doubt that he was walking in a straight line. It was a great moment 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, changed the idea that walking upright and increased intelligence evolved simultaneously.
“Lucy reinforced the argument that our ancestors learned to walk before they had larger brains and more advanced cognitive abilities,” said the paleoanthropologist.
A reconstruction of the appearance and bones of Lucy, a prehistoric woman who lived 3.2 million years ago. Credits: Cleveland Museum of Natural History Read more:
Fossil Lucy relatives carried tools 3.2 million years ago Human evolution revealed by 150,000-year-old shelter The “Stone Monkey theory” says the human brain evolved from human-like primates The discovery of River Lucy it also challenged the idea that human evolution was a linear process. Today, scientists compare the process to a “mighty tree,” with many branches representing different species. Some of these branches grew and evolved, while others were cut off abruptly.
Another metaphor, proposed by paleoanthropologist Andy Herries, is that of a “mixed river”, where the first humans met, adapted or disappeared. This approach explains phenomena such as the crossing between Homo sapiens and Neanderthals and the extinction of species such as Homo floresiensis, which lived in Indonesia until 50 thousand years ago.
Donald Johanson, responsible for the discovery of Lucy, named after the 1967 Beatles song "Lucy in the Sky with Diamonds", which was played loudly and repeatedly at the visiting camp. Credit: Institute of Human Origins/Arizona State University About Lucy, the world's most famous fossil:
The species was classified as Australopithecus afarensis, in honor of the local Afar people where it was found; Although he may not have been our ancestor, his discovery was fundamental in revealing the complexities of human evolution; Lucy's legacy also helped identify some ancient species of animals that coexisted around three million years ago. Although there are still gaps in the story, each new fossil discovered expands our knowledge of how we became Homo sapiens. For Johanson, Lucy is a symbol of this search. “It has become an evolutionary mascot, helping to build a richer, more detailed view of our origins.”