The Molecular Basis of Adaptation: A Critical Review of Relevant Ideas and Observations

accepted belief in the existence of an evolutionary process, this is a far cry from a precise understanding of the mechanisms involved. Indeed, a number of theories about the mechanisms of evolution have emerged over the years, but none has been completely satisfactory. By defini­ tion, any theory of evolution is a theory of change. The essential question in its most basic form is, How does life get from state A to state B? A and B refer to anyone of the levels of biological organization which range from the amino acid sequence of simple polypeptides to the complex morphological, behavior­ al, and ecological characteristics of distinct species, to take two examples. Before the application of biochemical and molecl.lar techniques to evolu­ tionary questions that began in the mid-1960s (e.g. 52, 57), the apparent progression of biological