To say that the world is predictable and unchanging for generations is just plain wrong.
One year the winters are mild, the next year extremely harsh. Some summers are warm and mile, some summers are blazing hot and filled with violent storms. Some years winter comes early, some years it comes late.
There are droughts, floods, plagues of insects, hurricanes, tornadoes, typhoons, any number of natural phenomena that make life completely unpredictable; especially so for Neanderthals.
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All of these phenomena are completely predictable variants in the Neaderthal experience, as they survived for tens of thousands of years and lived through a lot of change. I don't mean that their physical world was unchanging, I mean their mental image of the world was unchanging. All their experience with everyday fluctuations of their living conditions, never brought about a change in their way of being, nor did they seek progress. In essence, they lived in a predictable world.