Human evolution is the process by which humans have changed over time. It is believed to have begun in Africa about 7 million years ago, with the evolution of Homo habilis. Over the course of millions of years, humans have evolved into a species that is physically and behaviorally distinct from other species on Earth. This process has included changes in body size and shape, locomotion, diet, and other life history traits. It has also included changes in brain size and structure, language development, and social organization.