BOOK REVIEW
The Tree of Earthly Life: An Excerpt from I Have Landed
I would nominate as most worthy of pure awe—a metaphorical miracle, if you will—an aspect of life that most people have never considered, but that strikes me as equal in majesty to our most spiritual projections of infinity and eternity, while falling entirely within the domain of our conceptual understanding and empirical grasp: the continuity of etz chayim, the tree of earthly life, for at least 3.5 billion years, without a single microsecond of disruption.
Consider the improbability of such continuity ...: Take any phenomenon that begins with a positive value at inception 3.5 billion years ago, and let the process regulating its existence proceed through time. A line marked zero runs along below the current value. The probability of the phenomenon’s descent to zero may be almost incalculably low, but throw the dice of the relevant process billions of times, and the phenomenon just has to hit the zero line eventually.
For most processes, the prospect of such an improbable crossing bodes no permanent ill.... But life represents a different kind of ultimately fragile system, utterly dependent upon unbroken continuity. For life, the zero line designates a permanent end, not a temporary embarrassment. If life ever touched that line, for one fleeting moment at any time during 3.5 billion years of sustained history, neither we nor a million species of beetles would grace this planet today?.
... DNA has been working all this time, without an hour of vacation or even a moment of pause to remember the extinct brethren of a billion dead branches shed from an evergrowing tree of life.
From I Have Landed: The End of a Beginning in Natural History
Stephen Jay Gould
Harmony Books, $25.95
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