Final answer:
Selective breeding of domestic cats with African servals could change the genetic makeup of the domestic cat species, affecting traits such as size and color markings. It does not result in one species evolving into another but can influence certain traits within the species.
Step-by-step explanation:
The long-term effect of selectively breeding domestic cats with African servals could be change in the genetic makeup of the entire domestic cat species. Selective breeding can have significant impacts on the health and genetic diversity of animals. As seen with the English bulldog, selective breeding for specific traits can lead to health issues and a narrowed gene pool, resulting in animals prone to conditions such as cancer and allergies. In the case of the Savannah cat, a hybrid domestic cat breed, the introduction of serval genetics into the domestic cat population could potentially affect the prevalence of certain traits, like color markings and size, within domestic cats as a whole through interbreeding.
However, selective breeding does not lead to the evolution of one species into another, such as servals evolving into domestic cats or vice versa. Such evolution would require a much more complex process over a very long period of time. Instead, selective breeding can influence the physical and behavioral traits within a domesticated species, like inducing neoteny, the tendency to retain juvenile features.