The primary reason that natural philosophers began to classify humans into different races is that human populations look different from one another. Their skin colors, hair textures, facial structures, and stature all differ, often in predictable ways. Furthermore, these differences reflect their divergent geographical origins. In fact, researchers can classify human variation by continent quite accurately using only data from the human skull. (They are able to correctly classify human skulls into black and white Americans with about 80% accuracy, using only two variables.) Therefore, despite the common charge that racial classification is ipso facto racist, and that most Enlightenment typologies of human variety were motivated by prejudices and a desire to rationalize imperial domination, ordinary people and Enlightenment philosophers also took to classifying human differences for the mundane reason that such differences actually exist.