LONDON, ENGLAND—Bipedalism may have developed some seven million years ago as human ancestors foraged for food on flexible branches in treetops, according to a report in The Guardian. It had been previously suggested that hominins began moving on two legs in response to a shift in the environment from dense forest to more open woodlands and grasslands. Alex Piel of University College London and his colleagues tracked the movements of chimpanzees living in an open environment of woodland and grasses in western Tanzania’s Issa Valley, and determined that these primates spent a similar proportion of time on the ground as chimpanzees living in densely forested areas. “Even though we have far fewer trees, [the chimps are] no more terrestrial,” Piel explained. “Most of the time that they are on two legs is in the trees,” he added. This fits with the fossil record, Piel concluded, which indicates that early hominins had both arboreal and terrestrial adaptations. Read the original scholarly article about this research in Science Advances. For more on the evolution of hominin bipedalism, go to "The Human Mosaic."