Felidae is the biological family of the cats; a member of this family is called a felid. Felids are the most strictly carnivorous of the sixteen mammal families in the order Carnivora. The most familiar felid is the Domestic Cat, which first became associated with humans about 10,000 years ago, but the family includes all other wild cats including the big cats.

Extant felids belong to one of two subfamilies: Pantherinae (which includes the Lion, the Tiger, the Jaguar, and the Leopard), and Felinae (which includes the Cougar, the Cheetah, lynxes and the Caracal, along with the Domestic Cat).

The first felids emerged during the Oligocene, about 25 million years ago. In prehistoric times, there was a third subfamily Machairodontinae, which included the "saber-toothed cats" such as the well known Smilodon. There were also other cat-like mammals, such as Thylacosmilus or the Nimravidae which are not included in Felidae despite superficial similarities.

Evolution

There are 40 known species of felids in the world today which have all descended from a common ancestor about 10.8 million years ago. This taxon originated in Asia and spread across continents by crossing land bridges. As reported in the journal Science, testing of mitochondrial and nuclear DNA by Warren Johnson and Stephen O'Brien of the U.S. National Cancer Institute demonstrated that ancient cats evolved into eight main lineages that diverged in the course of at least 10 migrations (in both directions) from continent to continent via the Bering land bridge and Isthmus of Panama. The Panthera species are the oldest and the Felis species are the youngest. They estimated that 60 percent of the modern species of cats developed within the last million years. 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 felids' closest relatives are thought to be the civets, hyenas, and mongooses. All felid species share a genetic anomaly that prevents them from tasting sweetness.

Characteristics

Felids are purely carnivorous animals, subsisting almost entirely on other vertebrates. Aside from the Lion, they are solitary. Most are secretive animals, often nocturnal, and live in relatively inaccessible habitats. Around three-quarters of cat species live in forested terrain, and they are generally agile climbers. However, felids may be found in almost any environment, with some species being native to mountainous terrain or deserts.