India, Feb. 28 -- High in the forest canopy, long before we built cities or roads, life clung to branches.Our ancestors ate mangosteens and black junipers, crunched on nuts, and dug up tubers and roots. On an ill-fated day, one of them slipped and fell to her death from the same 40-foot-high canopy that nurtured her.

Three million years later, in what is now Ethiopia, her remarkably complete fossilised remains galvanised the world's interest in human origins. By 2016, Lucy, the bipedal hominin, had become an icon, her story pieced together by scientists who reimagined how she might have lived and died among the trees.

"Our ability to bounce along branches standing upright, our desire to build nests and smell cedarwood-all the adaptation...