'Natural selection merely modified while redundancy created'--Susumu Ohno's idea of the evolutionary importance of gene and genome duplications.

Susumo Ohno's influential book Evolution by gene duplication dealt with the idea that gene and genome duplication events are the principal forces by which the genetic raw material is provided for increasing complexity during evolution. In 1970, the evidence for this hypothesis consisted mostly of karyotypic information, crude information by today's standard genetic data, DNA sequences. Nonetheless, although the type of data are outdated, the idea remained current and is still debated today in the age of complete genome sequences. Even more than thirty years after the initial publication more research than ever is being carried out on the evolutionary significance of gene and genome duplications and the contribution of these mechanisms to the advances in genomic and organismal evolution.