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One-Way Evolution: The Ladder of Life Makes a Comeback
from New Scientist (Registration Required)
Celebrated palaeontologist Stephen Jay Gould once wondered what would happen if we could rewind the tape of life. If it were possible to turn the clock back half a billion years and then let evolution happen all over again, what would we see? Gould famously argued that the history of life would not repeat itself. The world would be unfamiliar, and would probably lack humans.
His point was to demonstrate that evolution is not a process of inexorable progress but of contingency. Mutations happen unpredictably. Sexual reproduction combines genes at random. Droughts, ice ages and meteorites strike without warning and kill off fully fit individuals and species.
We tell ourselves stories of evolutionary progress but these are just wishful thinking. Life produces abundant variations; most fail. The few that survive we call the most advanced, but that is a profound error which conflates "latest" with "best." As Gould wrote in his classic book Wonderful Life: "Life is a copiously branching bush, continually pruned by the grim reaper of extinction, not a ladder of predictable progress."
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