Anthropologist Frans de Waal has done experiments on bonobos and other primates to show that they use a type of morality. If one bonobo (bonobo A) sees that another bonobo (bonobo B) is being deprived of food, bonobo A may refuse to eat its own food as protest against bonobo B's treatment. This phenomenon demonstrates that nonhuman primates express a form of morality and may help us understand where our own human morality comes from.