The human beings are different from each other in terms of size, colour and looks but are said to be of the same species (Homo sapiens) because they can interbreed to produce fertile offsprings (son and daughter). The earliest members of Homo sapiens have been traced back to Africa. Some of our ancestors stayed back in Africa and spread across these continents; other left Africa and slowly, spread across the whole earth. They moved forward and backward in groups, separately or in mixed groups at times. These groups of ancestors, like other species, lived their lives in then prevailing environment and developed genetic variation to become differently coloured with specific features of different geographical regions in modern times.
