Darwin's Doubt: The Explosive Origin of Animal Life and the Case for Intelligent Design

by Stephen C. Meyer

Starting in the autumn of 1979, at the European Molecular Biology Laboratory in Heidelberg, two venturesome young geneticists, Christiane Nüsslein-Volhard and Eric Wieschaus (see Fig. 13.1), generated thousands of mutations to investigate the genomes of tens of thousands of fruit flies (species: Drosophila melanogaster). They hoped to get them to divulge the secrets of embryological development. In technical jargon, Nüsslein-Volhard and Wieschaus performed “saturation mutagenesis” experiments. After feeding male flies the potent mutation-causing chemical (i.e., mutagen) ethyl methane sulphonate (EMS), Nüsslein-Volhard and Wieschaus bred the males with virgin females. They then examined the offspring larvae for visible defects. In generating many thousands of mutants, thereby “saturating” the Drosophila genome, Nüsslein-Volhard and Wieschaus induced variations in the small subset of genes that specifically regulate embryonic development. These regulatory genes normally control the expression of many other genes that build the fly embryo, progressively subdividing it into regions that will become the head, thorax, and abdomen of the adult fly. The EMS mutagen disrupts DNA replication, thereby mutating genes. These mutations affect the process of development, leaving visible defects in the fly larvae.