The domestic cat (Felis catus) is one of the most recently evolved species within the Felidae family.
The Felidae family have been split into three genera:
- Panthera (cats that roar – lions, tigers, leopards, snow leopards, clouded leopards and jaguars)
- Acinonyx (the Cheetah)
- Felis (all other ‘small’ cats)
However, the classification of the Felidae family is difficult, in part because of the difficulty in distinguishing species by their phenotype and morphology – they all look remarkably similar and, for example, it is extremely difficult for even trained experts to differentiate the skull of a lion from that of a tiger. More recent genetic investigations have suggested eight distinct clusterings or lineages within the Felidae family which could therefore form the basis of their reclassification in the future.
All cats have evolved as predatory hunting mammals with particularly keen senses of hearing, sight and smell. Anatomical characteristics such as the rounded head and skeletal structure suggest that all the 37 recognised species within the Felidae family evolved from a common ancestor, probably living in Asia around 10-12 million years ago. There has been a rapid expansion and diversity of the Felidae family during the past 10 to 11 million years and by 3 million years ago there was a wide variety of cats populating all regions of the earth except the Arctic, Antarctic and Australia. The rise and fall of sea levels over many millennia helped both to create conditions where Felidae species could migrate and occupy other geographical locations (when sea levels were low) and isolate the development of species (when sea levels were high). The widespread migration of ancestral cats was probably made easier by their natural behaviour to disperse and seek their own territory, and also the need to follow the prey species they hunted on.
Felidae are the most highly developed carnivorous hunters of all mammalian species. With the exception of lions, which live in groups, all other wild cats have developed as solitary animals with the ability to hunt and fend for themselves. Cats are territorial, developing their own area in which they hunt and marking out their territory mainly via scent. They come together mainly for mating.
Again with the exception of lions (where males have a distinctive mane), the appearance of male and female cats is very similar, although males tend to be slightly larger. They have five digits on the front feet, and four on the hind feet. The digits are protected by pads, which also help reduce sound when they are hunting. Other than the cheetah, all cats have retractable claws.
Cats have developed a wide range of coat colours – under natural conditions, these are adaptations to allow the cat to be camouflaged and assist its hunting lifestyle.
Evolution and adaptation of Felis catus
Co-existence of cats and humans is evident from fossil records from early human settlements, although these have been assumed to be wild cats. The development of true domestication (or perhaps more accurately ‘taming’ of cats) was previously thought to have occurred in Egypt around 3600 years ago. Skulls of cats found in Egyptian cat burial grounds (called Mau by the Egyptians) have been identified as mainly being of the species Felis sylvestris lybica (the African wildcat) and it is this wild cat living in Asia and North Africa that is now thought to have been the major ancestor of the modern-day Felis catus. However, more recent evidence shows that feline domestication probably occurred about 10,000 years ago or more in the Middle East, in the region of the Fertile Crescent. The earliest true record of domestication comes from a cat that was found deliberately buried with its owner in a grave in Cyprus, some 9500 years ago, and it is assumed that domestication will have begun some time before this as there were no native cats on Cyprus.
Living near people
The first evidence of human stores of grain come from Israel about 10,000 years ago, and it is known that the development of grain stores caused an accumulation and rise in the population of the house mouse. It is this rise in the rodent population that is thought to have first attracted wild cats into close proximity with humans and then led to their subsequent taming. Cats more tolerant of humans would have been more likely to come close to human settlements, and this self-selection would have helped in the process of their taming and domestication.
Archaeological evidence suggests that cats were commonly found in association with human settlements in the Fertile Crescent (Israel and the surrounding countries) by 3700 years ago, and they became an ‘official deity’ (in the form of the goddess Bastet) in Egypt around 2900 years ago. Large numbers of cats were sacrificed to Bastet and mummified at that time, indicating that the Egyptians were actively breeding cats. By 2000 years ago there was increasing evidence of cats spreading throughout Europe.
Genetic analysis has demonstrated that the DNA of modern-day domestic cats throughout the world is almost identical to that of Felis sylvestris lybica, clearly showing that it is this species that gave rise to our domestic cats. The DNA from other small cats (including the European Wildcat (Felis sylvetris) and the Central Asian and Southern African wildcats (F s ornata and F s cafra) form distinct and unrelated clusters.
Felis sylvestris lybica still survives today and is a solitary nocturnal hunter with a similar appearance to domestic tabby cats, although a somewhat lighter (more sandy-coloured) coat. Individuals of this species are well dispersed across the savanna with large territories due to the relatively sparse availability of rodent prey.
The criteria of what defines a distinct species of animal are not entirely rigid. In general, different species cannot inter-breed, and do not do so under natural conditions. Under artificial conditions, it is possible to inter-breed some species of cats – e.g. lions and tigers, although the offspring are usually infertile. However, because of its close relation to the wildcat (Felis sylvestris), the domestic cat (Felis catus) still retains the ability to inter-breed with this species and this does occur under natural conditions with the resulting offspring being fertile. In some regions, this has caused significant problems with feral and stray cats inter-breeding with the native wildcat leading to a diminishing population of genetically distinct purebred wild cats (e.g. in Scotland and Hungary).
The domestic cat was first classified as Felis catus in 1758 by Carolus Linnaeus, and although this nomenclature is still the most commonly used, recent studies suggest that the domestic cat should really be regarded as a sub-species of the Wildcat – ie Felis sylvestris catus – and this term is used by some.
Domestication of the cat
Felis catus as a species has thus arisen through wildcats living closely with humans. However, this should not be regarded as ‘domestication’ in the same way that dogs and other animals have been domesticated. In general, cats have not undergone major changes during domestication and their form and behaviour remain very similar to that of their wildcat ancestors. They remain perfectly capable of surviving in the wild, and indeed many revert to a feral or wild existence.
The two main theories surrounding the domestication of cats are that either the original wildcats (Felis sylvestris lybica) were deliberately tamed and selected for friendliness, or that rather than being specifically selected they were more ‘tolerated’ by humans and gradually diverged from their ‘wild’ relatives through natural selection and adaptation to hunting the vermin found around human settlements. The latter is probably more likely, at least in the early stages of taming, as other animals such as ferrets and dogs would actually have been much more effective and efficient if human control of vermin had been the purpose. In either scenario, several traits of cats, including their small size, social nature, body language, love of play, high intelligence and perhaps an inborn tendency among all small felids towards tameness, may have facilitated their domestication.
For most other domestic animals, a much clearer and direct benefit to humans is evident, and in general (unlike cats) domestic animals are derived from herd or pack animals where humans have effectively taken over as the ‘alpha male’ and leader of the pack. The same cannot be said to be true of cats! Strictly speaking, most cats are not truly domesticated – this is defined as breeding, care and reproduction being totally controlled by humans producing a reproductively isolated population. This can only really be applied to pedigree pet cats, which from a very small proportion of the total pet cat population. Undoubtedly, one of the major attractions of cat ownership today is that while being tame, cats remain little altered from their wild relatives exhibiting many characteristics and traits that are mimicked in wild cats. Today’s domestic cats retain a number of characteristics from their desert-dwelling ancestors, including the ability to survive with a very low water intake through the production of very concentrated urine (more so than dogs) and the production of relatively dry faeces thus minimising water loss. They also tolerate extremes of heat, not showing signs of discomfort until skin temperature exceeds 52 degrees°C, whereas humans start to feel uncomfortable when skin temperature exceeds 44.5°C. There is also a lack of change in body temperature in the domestic cat during a 24 hour period (as they tend to be active both during the day and at night).