What's amazing about evolution is how mutation would enable an animal not simply to behave in a new way, but to judge situations in a new way: that is to judge instinctively that something desirable or undesirable is to engaged in a certain way. When I think of how much more difficult it is to imagine the cause of alteration of judgment, I can see why Darwin gave in to the temptation to resort to the Lamarkian notion of use/disuse to explain how human cognition evolves. To treat evolution merely in behavioral terms is them like robots or near zombies rather than as judging and experiencing animals.