Lucy, the 3.2-million-year-old human ancestor, walked upright with massive leg muscles.

Researchers have used the fossil of an early human ancestor named Lucy to recreate her muscles and determine how she moved 3.2 million years ago. The study, published in the journal Royal Society Open Science, found that Lucy's leg muscles were much larger than those of modern humans, enabling her to move freely between different environments. The 3D model also showed that Lucy could stand and walk as efficiently as modern humans, despite having a more platelike pelvis and shorter legs. Studying fossils of Australopithecus afarensis can provide insight into the evolution of bipedalism and when it emerged in early human ancestors.