Domestic cats are considered to be descended from the wild cat Felis silvestris, which is found naturally over much of Europe, Asia, and Africa, and which is one of the smaller members of the cat family. It is thought that the original ancestor of the domestic cat is the African subspecies, Felis silvestris lybca.Wild cats weigh about 3 to 8 kg (6 to 18 lbs) and domestic cats typically weigh between 2.5 and 7 kg (5.5 to 16 pounds); however, some breeds of domestic cat, such as the Maine coon, can exceed 11.3 kg (25 pounds). Some have been known to reach up to 23 kg (50 pounds) due to overfeeding. Conversely, very small cats (less than 1.8 kg / 4.0 lb) have been reported.Like all members of the Felidae family, cats are specialized for a life of hunting other animals. Cats have highly specialized teeth and a digestive tract suitable to the digestion of meat. The premolar and first molar together compose the carnassial pair on each side of the mouth, which efficiently functions to shear meat like a pair of scissors. While this is present in canines, it is highly developed in felines. The cat's tongue has sharp spines, or papillae, useful for retaining and ripping flesh from a carcass. These papillae are small backward-facing hooks that contain keratin and assist in their grooming.Cat senses are attuned for hunting. The senses of smell, hearing, and vision of cats are superior to those of humans. Cats' eyes have a reflective layer, which greatly improves their vision in dark conditions. They can not, however, see in total darkness. To aid with navigation and sensation, cats have dozens of movable vibrissae (whiskers) over their body, especially their face. Li (2005) reports that due to a mutation in an early cat ancestor, one of two genes necessary to taste sweetness has been lost by the cat family.Thirty-two individual muscles in the ear allow for a manner of directional hearing; the cat can move each ear independently of the other. Because of this mobility, a cat can move its body in one direction and point its ears in another direction. Most cats have straight ears pointing upward. Unlike dogs, flap-eared breeds are extremely rare. (Scottish Folds are one such exceptional genetic mutation.) When angry or frightened, a cat will lay back its ears, to accompany the growling or hissing sounds it makes. Cats will also turn their ears back when they are playing or to listen to a sound coming from behind them. The angle of a cat's ears is an important clue to their mood.Cats also possess rather loose skin; this enables them to turn and confront a predator or another cat in a fight, even when caught in a grip. The particularly loose skin at the back of the neck is known as the "scruff" and is the area by which a mother cat grips her kittens to carry them. As a result, cats have a tendency to relax and become quiet and passive when gripped there. This tendency often extends into adulthood and can be useful when attempting to treat or move an uncooperative cat. However, since an adult cat is quite a bit heavier than a kitten, a pet cat should never be carried by the scruff, but should instead have their weight supported at the rump and hind legs, and also at the chest and front paws. Often (much like a small child) a cat will lie with its head and front paws over a person's shoulder, and its back legs and rump supported under the person's arm.Like almost all mammals, cats possess seven cervical vertebrae. They have thirteen thoracic vertebrae (compared to twelve in humans), seven lumbar vertebrae (compared to five in humans), three sacral vertebrae like most mammals (humans have five because of their bipedal posture), and twenty-two or twenty-three caudal vertebrae (humans have three to five, fused into an internal coccyx).