Most felids have a haploid number of 18 or 19. New world cats (those in Central and South America) have a haploid number of 18, possibly due to the combination of two smaller chromosomes into one larger chromosome.
Prior to this discovery, biologists had been largely unable to establish a family tree of cats from the fossil record because the fossils of different cat species all look very much alike, differing primarily in size.
The felines' closest relatives are thought to be the civets, hyenas, and mongooses. All feline species share a genetic anomaly that prevents them from tasting sweetness.
Hybrids bred in captivity include the liger and the tigon. Ligers are larger than tigers.
Although the family Felidae is closely related to mongoose and hyaena, studies have found that they are, by genetic coincidence, the most closely related family to humans after other primates. If one were to take the genetic sequence of a human and change a small percentage of the genes, it would be identical, depending on the changes, to the genetic sequence of a domestic cat, or a lion, or any cat in between. If one were, however, to change a human sequence to match a dog's, or a rodent's, the process would involve a far greater number of genetic changes.
