Evolution
Although quantitative estimates vary widely, the consensus is that the history of the Earth is probably not unique. The figure of about one million "habitable" planets per galaxy is considered not unreasonable. Even if this value were overestimated by several orders of magnitude, it would still add up to trillions of potential cradles for life. If my reading of the evidence is correct, this means that trillions of planets exist that have borne, bear, or will bear life. The universe is awash with life.
p. 121
Christian de Duve Vital Dust: Life as a Cosmic Imperative
Basic Books, 1995

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