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No. 96: Nov-Dec 1994

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"ADAPTIVE" MUTATION

Six years ago, J. Cairns performed experiments with bacteria that implied that said bacteria could "direct" their own mutations so that they could cope more speedily with sudden environmental trauma. (SF#64) In Cairns' experiments, bacteria unable to digest lactose were presented with an all-lactose diet. They quickly acquired the mutations needed to digest the only food available. They did not have to wait for random mutations to accidentally hit upon the correct genome changes.

A firestorm spread across the scientific community, even though other researchers saw similar effects. It was traumatic! One of science's foundation stones was at risk. The current theory of biological evolution insists that all mutations are random. Cairns believed he had shown that his bacteria experienced only useful mutations. This claim was too awful to accept.

In the July 21, 1994, issue of Science, two new papers appeared that, while not proving that only useful mutations occur in Cairns-type experiments, do indicate that something unusual is indeed happening. Basically, when bacteria are under stress (say, starving), a "distinctive" type of mutation occurs! Is "distinctive" a code word for "non-random"? The title of the commentary accompanying the two articles says it all.

(Culotta, Elizabeth; "A Boost for 'Adaptive' Mutation," Science, 265:318, 1994.)

From Science Frontiers #96, NOV-DEC 1994. 1994-2000 William R. Corliss