Why does cross-fertilization usually create more genetic variation than self-fertilization?

Cross-fertilization creates more genetic variation than self-fertilization because it involves the recombination of genetic material from two distinct individuals. By combining the hereditary traits of two different parents, cross-fertilization produces offspring with a broader range of genetic diversity.123

In contrast, self-fertilization—the fusion of gametes produced by the same individual—tends to stabilize existing genetic strains and limits variability within a population. While self-fertilization can be a reliable reproductive strategy in stable environments, it often fails to provide the necessary genetic diversity for a species to adapt to environmental changes.23

The increased variability generated by cross-fertilization is essential for natural selection, as it provides a wider array of traits upon which selection can act. This capacity for variation ensures that, in a changing environment, some individuals may possess the traits required to survive, whereas populations relying solely on self-fertilization may lack the flexibility to adjust, potentially leading to an evolutionary "cul-de-sac".13