It is said that “necessity is the mother of invention.” Wheels and pulleys were invented out of necessity by the tenacious minds of upright citi zens. Looking at the history of mankind, however, one has to add that “Leisure is the mother of cultural improvement.” Man’s creative genius flourished only when his mind, freed from the worry of daily toils, entertained useless thoughts. In the same manner, one might say about evolution that “natural selection mere(y tnodifted, while redundanry created”. Natural selection has been highly effective in policing allege mutations that arise in already existing gene loci. Because of natural selection, organisms have been able to adapt to changing environments, and by adaptive radiation, many new species were created from a common ancestral form. Y et, being an effective policeman, natural selection is highly conservative. Had evolution been entirely dependent upon natural selection, only numerous forms of bacteria would have emerged from a bacterium. The creation of metazoans, vertebrates, and finally, mammals from unicellular organisms would have been quite impos sible, for such giant leaps in evolution required the creation of new gene loci with previously nonexistent functions. Only the cistron, which became redun dant, could escape from the relentless pressure of natural selection, and by escaping, it accumulated formerly forbidden mutations to emerge as a new gene locus.
