Your flexibility of mind is impressive, for a man of your evolutionary era. - Stephen Baxter

On the longest of timescales, over millions of years, the workings of chance defied human intuition. Humans were equipped with a subjective consciousness of risk and improbability suitable for creatures with a lifespan of less than a century or so. Event that came much less frequently than that—such as asteroid impacts—were place, in human minds, in the category not of rare, but of never. But the impacts happened even so, and to a creature with a lifespan of, say, ten million years, would not have seemed so improbable at all.
Given enough time even such unlikely events as ocean crossings from Africa to South America would inevitably occur, over and again, and would shape the destiny of life.

But even if it is true, even if we are governed by the legacy of an animal past, then it is up to us to behave as if it were not so.

I was struck by how ignorant we humans are, or make ourselves, of the passage of time itself. How brief our lives are!—and how meaningless the events which assail our little selves, when seen against the perspective of the great plastic sweep of History. We are less than mayflies, helpless in the face of the unbending forces of geology and evolution—forces which mold inexorably, and yet so slowly that, day to day, we are not even aware of their existence!