The constant expansion of the evolutionary paradigm has reached the point that no one author can feel competent to deal authoritatively with all its aspects. For this reason this book was written by four authors, each with markedly different but complementary interests and expertise. Although this has braodened the range of topics that could be expertly treated, we have by no means exhausted the gamut of evolutionary issues. Perhaps this is the last time that a reasonably comprehensive account of the theory of evolution can be encompassed in a single volume.