Adaptive Evolution of Genes and Genomes, by Austin L. Hughes. Oxford University Press, New York. 1999. 270 p. Hardcover. $60.00 ISBN 0-19-511626-7.
DNA sequence databases present increasingly abundant opportunities to study hundreds of millions of years of evolutionary history. The redundancy of the genetic code means that changes in protein-coding DNA sequences may be synonymous (resulting in no amino acid change, and thus presumably having little or no adaptive significance) or nonsynonymous (altering the amino acid sequence and possibly the function of the protein). Proceeding on the assumption that synonymous changes are neutral and nonsynonymous changes are subject to natural selection, Hughes outlines in his first 3 chapters how sequences of the same gene from different taxa reveal 3 possible types of molecular evolution: (1) synonymous and nonsynonymous changes are equally abundant, indicating selectively neutral change resulting from genetic drift; (2) synonymous changes are more abundant, indicating that selection has...