Constraints on the origin and evolution of life.

As an introduction to my topic, let me quote from the 1970 bestseller, Chance and Necessity, by the late Jacques Monod. In this “essay on the natural philosophy of modern biology”, as the book is subtitled, the celebrated French biologist attempted, as many have done before and after him, to derive some sort of Weltanschauung from the science of his day. On the existence of intelligent life on Earth, Monod wrote the famous sentence: “The Universe was not pregnant with life; nor the biosphere with man”.2 He did not mean this literally, of course, considering that the Universe did give birth to life and the biosphere did give birth to human beings. Birth without pregnancy would imply a miracle, which is certainly not what Monod had in mind. What he meant is that life arose through the combination of highly improbable circumstances, so improbable that life may have arisen only once in the whole history of the Universe and might well, but for a fantastic stroke of luck, never have arisen at all. Given the fact that life did arise, the probability that it would evolve into intelligent beings is once again, according to Monod, extremely low. In other words, we owe our existence to the succession of two extremely improbable events, a near-miracle squared, so to speak, a cosmic quirk. And Monod concludes: “Man knows at last that he is alone in the Universe’s unfeeling immensity, out of which he emerged only by chance”.3 Beautiful poetry, but somewhat shaky science. I propose to explain briefly why I disagree with my late friend Jacques Monod.4