Fact and Fiction

Theories of Evolution

More than 500 million years ago, when all the continents were still only one gigantic mass (Gondwanaland) sharks and man shared a common ancestor, a certainty accounted for by successive theories of evolution.  After Linnaeus and Lamarck, Darwin and the Neo-Darwinists arrived at a theory which was endorsed by the majority of scientists, that of mutation followed by selection by the natural environment.  On a temporal and statistical level, some find it hard to see how this pattern of mutations and successive selections, even over millions of years, could have caused the living creature to change from a single-celled organism into a hypersophisticated mammal with highly complex organs and an extraordinary adaptation.

Among the many "schismatic" theories expressed is that of Motoo Kimura of Japan, who considers evolution to be the fruit of the accumulation of random micromutations rather than the result of the selection of the best of them.  He considers that the majority of genetic mutations have no visible effect on living organisms, and therefore believes that they could only be brought about by chance.

Kimura looks for the cornerstone of his anti-establishment theory on the floor of the oceans, in the genes of the Port Jackson Shark.  This fish's anatomy (see the Directory of Sharks) has remained the same for 300 million years, as a great number of fossils prove.  Now, it so happens that this bottom-dwelling, very sedentary shark, possesses a globin (a blood protein used for fixing oxygen) which has been well studied, and which has changed as much as that of man, who himself the fruit of continuous natural selection.  Kimura deduces from this that "nature" cannot have exerted any natural selection on the globin, and therefore calls into question Darwin's theory.  He calls his bombshell "the neutralist theory".

Whatever the future of this theory, sharks will play a part in attempts to prove it, since they are the animals that have evolved the least since they first appeared, as if chance had made them at the very start perfectly adapted to their environment.