Behavioral ecology investigates the relationship between the environment and animal behavior. It emphasizes the evolutionary roots of the behavior, in contrast to the classical studies involving animals in laboratory settings. American biologist George C. Williams (1926–2010), in his book Adaptation and Natural Selection (1966), first posed the question as to how behavior affects evolutionary fitness. By showing that behavior is responsive to the environmental forces that drive natural selection (and evolutionary fitness), researchers have demonstrated that the environment plays a crucial role in determining which behaviors are exhibited in natural settings.