Nature is forcing genetic drift to move faster in mating systems than in other bodily functions. If this is generally true, as Goodenough observes, it means that genetic drift in mating systems must have a special importance as a driving force of evolution. She proposes a general theory to explain the facts. In the big picture of life evolving over billions of years, established species with large populations evolve slowly and have a mainly conservative effect on the balance of Nature. The big jumps in evolution occur when established species become extinct and new species with small populations diversify. The big jumps, made by new species, are driven by genetic drift of small populations. For small populations to form new species, they must become genetically isolated. Rapid change of mating systems is a quick road to genetic isolation. Goodenough concludes that the rapid mutation of mating-system genes is Nature's way of achieving big jumps in large-scale evolution. Rapidly evolving mating systems gave us the diversity of species that astonished Darwin.

The picture of Nature revealed by Kimura and Goodenough is new and striking. Nature loves to gamble. Nature thrives by taking risks. She scrambles mating-system genes so as to increase the risk that individual parents will fail to find mates.