The ancestors of humans may have begun moving on two legs to forage for food among the treetops in open habitat, researchers have suggested, contradicting the idea that the behaviour arose as an adaptation to spending more time on the ground.The origins of bipedalism in hominins around 7m years ago has long been thought to be linked to a shift in environment, when dense forests began to give way to more open woodland and grassland habitats. In such conditions, it has been argued, our ancestors would have spent more time on the ground than in the trees, and been able...