Fifty years on, how Lucy, the mother of humanity, changed our understanding of evolution

In 1974, the fossilised bones of Lucy, a 3.2 million-year-old hominin, were discovered in Ethiopia. How has this remarkable skeleton disproved Darwinian theory - and what links her to the Beatles?

On 24 November 1974, the US anthropologist Donald Johanson was scrabbling through a ravine at Hadar in the Afar region of Ethiopia with his research student, Tom Gray. The pair were looking for fossilised animal bones in the surrounding silt and ash when Johanson spotted a tiny fragment of arm bone - and realised it belonged to a human-like creature.

We looked up the slope," Johanson later recalled. There, incredibly, lay a multitude of bone fragments - a nearly complete lower jaw, a thighbone, ribs, vertebrae, and more! Tom and I yelled, hugged each other, and danced, mad as any Englishman in the midday sun!"