The presumed opposition of nature and nurture has been a major concern of western civilization since its beginnings. Christian theologians interpreted Adam and Eve's eating of the forbidden fruit as the origin of an inherited 'original sin'. Saint Augustine explicitly applied the concept to human mental development, arguing that, because of original sin, children are inclined toward evil and education requires physical punishment. For centuries, it was considered parents' moral and religious obligation, not to nurture their children, in our current sense of that word, but to beat the willfulness out of them. 16thC humanists fought back, arguing that "schools have become torture chambers" while it is adults "who corrupt young minds with evil". Locke's (1690) statement that children are born as a 'white paper' was crucial in rejecting the dogma of an inborn (and sinful) nature. The original sin vs. white paper argument merged with another ancient dichotomy: inborn instinct (which controls animal behavior) vs. the reason and free will which humans have. Darwin made the concept of inherited instinct, common to both man and animals, one cornerstone of his theory of evolution. The 20(th)C saw scientists recast the debate as instinct vs. learning, bitterly argued between behaviorists and ethologists. Laboratory experimentation and field observation showed that behavior could develop without learning but also that conditioning paradigms could powerfully mold behavior. The progress of genetics and neurobiology has led to the modern synthesis that neural development, and hence behavior, results from the interdependent action of both heredity and environment.