"IN SHORT, three concepts, evolution, in the minimal sense of "descent with modification" (no "emergence," no "higher and lower" allowed), variation, in the sense of Mendelian micromutation, tiny changes in the structure or arrangement of the genes, the ultimate material of heredity (no sweeping or sudden alterations allowed), and natural selection, the decrease in frequency of those variants that happen in each successive generation to be less well adapted than others to their particular environment: these three form a tight circle within which, in happy self-confirmation, neo-Darwinian thinking moves. To those who believe in it, this circle is an ample intellectual dwelling place, roomy enough in fact to house all the immense achievements of modern biological research. To those not so convinced, however, the circle seems a strangely constricted one. They may even agree with the Professor Emeritus of Zoology at Cambridge that ‘no amount of argument, or clever epigram, can disguise the inherent improbability of orthodox (Darwinian) theory.’"