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No. 41: Sep-Oct 1985

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Evolution's motor runs fast and quietly

M. Kimura has been promulgating what he terms The Neutral Theory of Evolution. He concludes that "the most prev-alent evolutionary changes that have occurred at the molecular level, that is in the genetic material itself, since the origin of life on Earth are those that have been caused by random genetic drift rather than by positive Darwinian selection." Kimua maintains and can experimentally prove to some extent that the genetic material of all organisms changes rapidly and constantly. The genes change much more rapidly than scientists believed just a few years ago. We observe few if any changes at the phenotype level (organism morphology) because the overwhelming majority of these changes are neutral. They confer no significant advantage or disadvantage on the organism. In fact, Kimura and others have demonstrated that the fastest molecular evolution occurs in the least important genes. It is fastest of all in the pseudogenes or dead genes, which seem to have no discernable functions. In other words, the genetic engine is running, but the gears are in neutral!

In Kimura's thinking, these molecular changes may eventually become important at the phenotype level if the environment changes or there is some other destabilizing influence. Kimura is the author of the 1983 book The Neutral Theory of Molecular Evolution. Although Kimura has some experimental support, his theory is not widely accepted.

(Motoo Kimura; "The Neutral Theory of Molecular Evolution," New Scientist, p. 41, July 11, 1985.)

Comment. The intriguing part of Kimura's article concerns that steady hum of gene changes -- all to little or no avail when times are stable--but seemingly ready to provide the genetic pressure required to fill new niches. Why do these nonliving molecules have just those properties vital to life? It hardly seems sufficient to say that if nonlife did not have the properties it has we wouldn't be here. It raises again the question of whether the human blueprint is implicit in the electron and other simple particles. If so, what blueprints reside there still unrealized?

From Science Frontiers #41, SEP-OCT 1985. 1985-2000 William R. Corliss