The Problem

The maintenance of genetic diversity is probably the most fundamental issue in population genetics. Only one generally accepted way exists for generating diversity — mutation — and there is only one force shaping the overall course of evolution — natural selection. There is no doubt, however, that the picture revealed by study of natural populations is quite incompatible with the suggestion that if most genetic loci are selected the diversity is simply the result of the balance of mutational input and selective elimination. There is far too much polymorphism for this to be true. There is also a great ability to respond in an adaptive manner to new environmental conditions, almost as if a high level of polymorphism is maintained for the purpose of making such responses possible. The central problem is to determine the purposeless combination of factors that brings this situation about. The literature of population genetics has circled round this issue for at least fifty years, and it is perhaps not too frivolous to compare the situation with one which arises in a science fiction novel called the Hitch Hiker’s Guide to the Galaxy (Adams 1979). An immensely powerful computer called Deep Thought is set the task of finding the answer to the Ultimate Question of Life, the Universe and Everything. After an enormously long time it comes up with the answer, which turns out to be 42.