As hybrids, bengals and savannahs both were bred by humans. This breeding has sparked controversy over whether these cats should be bred at all since they do not occur naturally in the wild, as well as whether or not these hybrids should be considered domestics or exotics.
In 1963, Jene Mill, in conjunction with Dr. Willard Centerwall, bred an Asian Leopard Cat with a domestic short hair, resulting in the first documented bengal cat. This breeding was the end product of a study, conducted by Dr. Centerwall, of the Asian Leopard Cat's natural immunity to feline leukemia, a trait which Dr. Centerwall had hoped would pass to the Bengal cat. Whether or not the cats are immune to feline leukemia is still widely debated; however, Dr. Centerwall’s research did not find any evidence of immunity in the Bengal cat, which led him to work with Jene Mill to bred the hybrid for domestic purposes.
The breeding of the Bengal cat is controversial in many respects, but the controversy, in part, stems from the fact that this breed is the result of scientific experiment in which cats where bred to determine if the immunity to feline leukemia could be passed. Another cause for the species' controversy is the Bengal's risk of inbreeding and health complications resulting from inbreeding, including cataracts, progressive retinal atrophy, and cardiomyopathy.
The first Savannah cat was documented in 1986, and, since then, the savannah cat has been a controversial breed. In fact, savannah cats are illegal in New York City, Massachusetts, Hawaii, and Georgia, and are regulated in many other states. This is partially due to their breeding.
Savannah cats are sold by their generation, F1 through F5. The F1 generation is the direct result of breeding a Serval with domestic, and is 50% Serval. The following generations are the result of an earlier generation being bred with a domestic, and progressively have more genes in common with the domestic cat. For example, an F2 is the product of an F1 and a domestic being bred, and is 25% Serval, while an F3 is the product of an F2 and a domestic and is only 12.5% serval.
Since the selling value and exoticness of a Savannah depends on how many genes it shares with a Serval, Servals have to be used to breed new lines in order to meet the demand for Savannah cats. While this does prevent inbreeding, there is concern about holding Servals in captivity for the breeding of an exotic-domestic. Furthermore, the F1 generation's 50% similarity to the Serval raises concerns about their temperament. While Savannahs are commonly bred for temperament and raised as domestics, some are concerned that their wild genes could lead to natural instincts emerging, which could cause problems for owners or even the ecosystem if a number of these cats escaped.