Human evolution is tightly connected to the environment and landscape of Africa, where our ancestors first emerged.
According to the traditional scientific narrative, Africa was once a verdant idyll of vast forests stretching from coast to coast. In these lush habitats, around 21 million years ago, the earliest ancestors of apes and humans first evolved traits – including upright posture – that distinguished them from their monkey cousins.
But then, the story went, global climates cooled and dried, and forests began to shrink. By about 10 million years ago, grasses and shrubs that were better able to tolerate the increasingly dry conditions started to take over eastern Africa, replacing forests. The earliest hominins, our distant ancestors, ventured out of the forest remnants that had been home onto the grass-covered savanna. The idea was that this new ecosystem pushed a radical change for our lineage: We became bipedal.
For a long time, researchers have linked the expansion of grasslands in Africa to the evolution of numerous human traits, including walking on two legs, using tools and hunting.
Despite the prominence of this theory, mounting evidence from paleontological and paleoclimatological research undermines it. In two recent papers, our multidisciplinary team of Kenyan, Ugandan, European and American scientists concluded that it is time finally to discard this version of the evolutionary story.
