Many wild and cultivated plants arise through the combination of two species. The genome of these so-called polyploid species often consists of a quadruple set of chromosomes—a double set for each parental species—and thus has about twice as many genes as the original species. About 50 years ago, evolutionary biologists postulated that this process drives evolution, leading to new species. Due to the size and complexity of such genomes, however, proving this theory on a genetic level has been difficult.