Lucy’s contribution: Understanding the sequence of steps leading to human uniqueness

Humans are a spectacular outlier among the millions of species of life on planet earth, with incredibly unique biological success. Slowly, scientists have begun to understand the traits that interacted to make us unique, such as cumulative culture, unique scales of cooperation, cognitive abilities, language, and a unique life history and mating system. However, the sequence of evolutionary events that led to our unique species was very much a mystery until the discovery of early bipedal hominins like the australopithecine, Lucy. Here I will explain how we have learned so much about this improbable sequence and evolutionary pathway by discovering that early hominins were fully bipedal but still had small brains and little evidence for human mating and life history patterns or cumulative cultural evolution. Lucy helped us understand why the evolution of bipedality was a critical first step that led to an amazing evolutionary sequence that resulted in our spectacular outlier species.