Retorts

Evolution Example

Your recommendation to Renton Maclachlan [Retorts, May] that he should read Dawkin's The Blind Watchmaker is excellent advice.

"The assumption of evolution is almost universal". This is so for the same reason that ships' captains and aircraft pilots do not sit around arguing whether the Earth is flat; they get on with the job of navigating their craft about the oblate spheroid on which we all live. The evidence for evolution is now so overwhelming that biologists have stopped asking "Whether?" in favour of answering in more detail the more difficult and interesting question "How?".

Your correspondent's first question on the basic mechanism of evolution is answered in the Dawkins book and many other texts. To his second -- on how non-living matter gave rise to life -- the answer given by honest scientists is "We don't know, but we are looking hard". Mr Maclachlan's view of this most basic biological question would seem to preclude any expectation of reaching a conclusion. The picture of the first replicators he seems to have in mind in posing his third question is a much more highly developed, and therefore more unlikely, organism than biologists of today imagine.

Yes, one can see evolution taking place in the world today: until the 1940s, insects had existed for millions of years with no contact with synthetic insecticides, because, as far as we know, they did not occur on Earth. Yet within a few years of the widespread use of DDT, strains of insects appeared which were resistant to it. They had acquired a gene coding for an enzyme able to convert the hitherto non-existent DDT into a harmless substance. Where did this gene come from? Was it a gift from insect heaven? A more probable explanation is that insects already possessed an enzyme fulfilling an ancient and well-established role in detoxification. Mutation in one or a few individuals could subtly change the enzyme so that it could attack the new substance. By natural selection the gene for this enzyme would spread through the population.

The necessity for Mind to create coded information, a matter troubling Mr Maclachlan, is dealt with, and convincingly disposed of, in another book to be highly recommended -- Daniel Dennett's Darwin's Dangerous Idea. In Dennett's view, Darwin's idea was not only dangerous, but probably the best idea anyone has ever had.

Professor Bernard Howard, Christchurch