A predictable animal is a dead animal. Unpredictability has survival value. This is true when dealing with other animals and also when dealing with the rest of the world. When the world around them changes humans can change to compensate. Animals can too but biological evolution may be too slow in which case the animal dies out. And even if the species manages individual animals will die along the way. We get the jump on evolution by consciously adaptating our social structure, as well as our individual behavior.
Evolution can produce anything with survival value. Nature doesn't care if we understand. We don't "understand" quantum mechanics either, that is, portions of it do not make everyday sense, but it's there, proven a gazillion times over. Free will gives us maximum unpredictability. In fact, the future actions of a free will being are unknowable even to God, never mind a cave bear. We possess free will as evidenced by the fact that we can outwit any other animal. The fact that we may never understand how it works is immaterial.
Cause and effect is a feature we humans ascribe to the world. Some other apes seem to have a notion of it as well. Yet if you look at the world much of it seems random. We just assume that if we knew enough we could assign all the requisite causes. But quantum mechanics has blown that idea out of the water, so why do materialists insist on it?
OK enough of my blather. Keep yours coming though. I love these kinds of articles.