Although it can be said that the precise origin of the domestic cat may never be fully known, unless some unexpected archaelogical discoveries are made, it is nonetheless possible to draft a broad outline of the probable domestication of the animal and its subsequent evolution. The cat has managed to fill a unique socioecological niche opened by the rise of civilized man.

Domestication 

For hundreds of thousands of years man was a hunter-gatherer, nomadic or semi-nomadic in behaviour. This existence slowly changed, probably as a consequence of several factors, such as, climatic change, increase in population density, slow exhaustion of game and cultural evolution. In round figures, modern civilization in terms of an agricultural-based economy, domestication of animals and the appearance of towns began approximately 10,000 BC.

One of the most successful, as judged by achievement, was that arising in the Middle East , in a region around the eastern shores of the Mediterranean and extending as far as the Caspian Sea and Persian Gulf . The earliest remains of almost all of the major domesticates (cattle, dogs, goats, pigs and sheep) are to be found in the region. It is usually assumed, with some justification, that the young of likely species would be confined, and only those amenable to confinement, adaptable to close proximity of others of the species and of man would survive. In effect, this means species with strong social tendencies (herd or pack-forming species). The motive of the early domestication was the provision of meat. Later, the whole animal was utilised in one way or another.

It is almost impossible to assess if the cat featured in the early period of domestication. Probably not in any deliberate sense, yet a biological niche had been created by early civilisation. Settled farming and stock keeping implied granaries and barns, and the mouse, Mus musculus, quickly adapted itself. Aboriginal mice became the commensal house mouse about this time. Protected from its usual predators, the house mouse could have been a troublesome pest, as judged by the masses of skeletons recovered from the basements of dwellings of Middle East archaeological sites. It is not unreasonable to postulate that the cat may have followed the mouse and become a scavenger around farms and villages. The relationship between cat and man would have been uneasy initially but tolerated by the latter as a means of curbing the ravages of mice.

One murine researcher has suggested that the cat may have been domesticated in order to combat epidemics of mice. This could be the case but it may imply more purposeful behaviour on the part of man than that which probably occurred. It is conceivable that young kittens could be reared in captivity but much would depend on how far the cat had adapted to man. It would be easy to postulate that the tamer of these cats would stay while the wilder would depart, in this manner the cat may have entered domestication. It would be impossible to assign dates to the event but the above concept would indicate that it would be desultory and probably extended over a long period. Even a semi-wild cat shut in a granary could curb the activities of the mouse population.

A development now occurred which transformed the situation, the Egyptians were emerging as influential people in the Middle East who were greatly interested in animal life. They had a penchant to associate gods with specific animals. In particular, the male cat was depicted as sacred to the sun god Ra and the female cat to the fertility goddess Bast, two potent deities of the age. This was approximately 4,000 BC and, about this time, the cat had attained an important position in religious life, so much so that the animal itself became deified. Since it was desirable to show respect to the gods, the keeping of cats became common throughout Egypt . Not only were they carefully tended during life but the cadaver was preserved in special cat cemeteries covering many acres.

The high point of cat keeping for the region was about 3,000 BC, the species was so abundant that it was being depicted in countries beyond the borders of Egypt . For example, in Crete (2,900 BC), mainland Greece (2,500 BC), Libya (2,500 BC), India (2,300 BC) and China (2,200 BC). Note the dates which roughly chronicle the spread of the cat throughout the extent of the world which had attained a level of culture able to support an aesthetically pleasing household pet. The invasion and subduing of Egypt by the Romans and the rise of Christianity freed the cat from religious connotations and allowed the animal to become a domestic pet. The Romans are held responsible for the cat reaching Europe ( Italy , 1,900 BC, Switzerland , 1,800 BC, Germany , 1,000 BC and Britain , 1,600 BC). Again there is evidence of a slow migration.

The domestication of the cat, with special regard to Egypt is summarised as follows:

•  Period of competition (prior c.7,000 BC), characterised by wild cats competing with man (hunter/gatherer) for birds and small mammals.

•  Period of commensality (c.7,000 to 4,000 BC), characterised by 'semi-domestic' cats feeding on vermin around and within the early villages.

•  Period of early domestication (c.4,000 to 3,000 BC), characterised by the confinement of cats for cult purposes.

•  Period of full domestication (c.3,000 BC onwards), characterised by the great popularisation of cat keeping within Egypt and the earliest diffusion of the animal from Egypt.

The summary calls for two comments from a genetical viewpoint. First, the period of commensality would indicate variability of fearsome behaviour (to man at least) for certain individuals to venture into the villages. Second, the capture of these animals would induce intense selection for cats which could adapt to confinement, tolerate close proximity of man and rear kittens in such an environment. Puberty in the species depends partly on the month of birth of the kitten, but if a period of one year is assumed, the difference in numbers of years will give a good approximation to the number of generations involved. Therefore, the periods can be reckoned in terms of thousands of generations. These would be ample for the observed genetic changes to have occurred.

Apparently there is a long tradition of carrying cats aboard ships as charms for a safe voyage, as companions and to combat vermin. By this, man has unwittingly aided the migration of the animal, thus, expanses of water are not a barrier, as is the case for most land animals. On the contrary, busy sea lanes are veritable highways for the cat, especially with the progressive increase in maritime travel and commerce over the centuries. The expansion into the New World and Australia was by sea as a direct consequence of the rise of ocean-going ships and human colonisation. This aspect will be further discussed anon.

The biological route by which the cat was domesticated would seem to be one or more of three possibilities. These are (1) by a form of neotony by which juvenile characteristics persist into the adult, particularly behavioural which encourage dependency, (2) modification of hormonal balance, mainly by reduction in size of the adrenals and their secretions, and (3) reduction of brain size, thereby impairing the animal's sensitivity to uncongenial stimuli. Routes (1) and (3) may be correlated, as indeed all three may be to some extent.

Among the races of silvestris , the European had the largest brain, followed by the steppe cats of central Asia and lybica of north-east Africa . A group of mummified Egyptian cats possessed a brain identical in size to lybica. However, skulls from mediaeval Russian cities showed a fall in brain size, a trend which was continued by a stock of Siamese. Hemmer (1976b) suggests that the main decline was of the order of 10 and 15 per cent respectively. Two groups of domestics (normal and feral) exhibited a wide range of brain sizes, from that of lybica to beyond that of the Siamese. Very few of the domestics approached the brain size of European silvestris . It would seem that the contribution of silvestris to the modern day cat is either lacking or negligible. Also, it is probable that there has been a reduction in brain size as a concomitant of domestication. It is questionable whether the reduction can explain all of the present day docility, but it may be contributory.

It is difficult to speculate that some interbreeding between wild cats and domestics took place, given the unconfinement of the latter. European silvestris has the reputation of being a shy, reclusive animal, at least in regard to man. This is not necessarily a universal trait, of course, and populations may vary in this respect. Popular reports of wild cat kittens being timid yet tamable should be regarded with some disbelief. These could be feral domestics because even the kittens of the household females must be socialised with man at an early age if these are not to display some fearful behaviour as adults. Even if the kittens are wild cats, it is possible for them to have some domestic ancestry, thus explaining their amenability.

The lybica form is common in Rhodesia and can be domesticated, perhaps more easily today than in the past. Many now slink about in semi-urban areas, interbreeding freely with the domesticated form. Such populations would be an 'in between' form of the true wild cat and feral cats (domestics which have returned to the wild) but for the most practicable purposes being indistinguishable from the former. If the process has been underway for some time, a new type of cat would be evolving, wild in appearance but more adaptable to an emerging environment of mixed farming and cultivated land, with some admixture of semi-urbanisation.

Monophyletic origin 

The wild ancestor of the cat must be sought in the Middle East and is almost certainly the subspecies Felis lybica of the F. silvestris species complex. These constitute a group of small wild cats inhabiting Europe , Asia and North Africa , all of which are similar in appearance and size. At one time it was thought that the two forms, ( silvestris and lybica ) were distinct species but this opinion is no longer tenable. They will interbreed with each other and with the domestic cat and produce fertile offspring. Their karyotypes are identical. Both species are phenotypically mackerel striped tabby and such differences as exist are due to adaptation to different geographical environments.

It has been suggested that the domestic cat may have a polyphyletic origin or, more precisely, polyspecific. This seems unlikely. The only species worthy of consideration in this connection is F.chaus and for two reasons. While the majority of European mummified skulls examined could be attributed to a race of F.lybica, a small proportion could be attributed to F.chaus. The karyotype of F.chaus is identical to F.lybica, hence hybridisation is possible and has been realised on occasion. However, the existence of mummified chaus skulls merely means that the species was kept in captivity, not necessarily that it was domesticated. F.chaus is a larger animal than lybica and the two species would probably not normally copulate. Unless observations are biased by accidents of sampling, the low proportion of chaus skulls (3/192=0.016) would imply that the species was rare and any contribution it may have made to the cat gene pool would have been swamped by the lybica influence.

One of the more plausible arguments for ancient hybridisation is that chaus has a vestigial tabby pattern and it has been conjectured that chaus might be responsible for the Abyssinian pattern. However, this view will not withstand critical examination. The Abyssinian pattern is inherited as an allele at the tabby locus and almost certainly arose by mutation, not by hybridisation. Also, probably at a much later date since preliminary censuses of mutant phenotypes in modern Egypt and Sudan have failed to detect the Abyssinian pattern.

Population genetics 

The world-wide census of cat coat colours which has been in progress for over a decade has revealed a number of interesting features. Most of the observed mutants must be of ancient origin, as evinced by their global distribution. Those mutants which fall into this category are non-agouti (a), blue dilution (d), long hair (l), sex-linked orange (O), piebald (S), blotched tabby (tb) and dominant white (W). These are the most common mutants used in the surveys but there are others (to be considered later). That man was the main preserving agent is difficult to prove directly but there are two points in this direction. The brighter the colour or the more obvious the effect (eg. long hair), the more likely the preference. The second is that mutant phenotypes are often regarded as hallmarks of domestication.

The frequency distribution of individual mutants is not uniform throughout the world. Some alleles have a low or moderate frequency of occurrence in most geographical regions, such as d and S. The l allele was thought to be similarly distributed but recent observations suggest that it may occur with elevated frequency in Turkey , possible Iran , but particularly in Russia. One can only surmise at present that the long hair may offer some protection from the cold.

The a allele is remarkable because it occurs at a high frequency in all parts of the world, in some regions at especially high frequencies. The reason for this is not directly known but a possible explanation is that all-black phenotypes may be less fearful than wild type. A gene conferring a degree of placidity would possess an advantage under conditions of domesticity, particularly if it arose early in domestication. At this time, all phenotypes in the cat are docile, due to the accumulation of 'taming' genes, hence the advantage may be less now than formerly.

The O allele occurs at its highest frequencies in the East, (India , South-east Asia and Japan). It has been proposed that the allele may have arisen in the East and is diffusing westwards. This could be the case since the orange phenotype is attractive. However, the allele also displays an inverse relationship with the dark phenotypes produced by a and tb, as if environments favouring these latter two alleles are not altogether congenial to O. This relationship complicates a simple explanation for O.

The explanation for the high frequency of t b in Britain is obscure, It is tempting to postulate that the mutant occurred in Britain and is subsequently spreading around the world, aided by the fact that Britain is a maritime nation. This is possible but by no means certain. In any event, the apparent advantage of t b remains unresolved. The only hard evidence is that the allele may have increased relatively rapidly in Britain over the last few centuries. It coincides with the growth in human population density (and that means cat population density) and this may be the clue. The advantage of t b may be density dependent and be linked to the suggestion that melanotic mutants are less fearful. If t b is density dependent, this may explain why the allele has not increased in the former British colonies to the same level as found in modern Britain . The allele could be increasing but only after a time-lag representing the period between the initial colonisation and the growth of population density to the stage where the density dependent advantage can be effective.

It is difficult to imagine that the exceptionally high values of tb in Britain are due solely to human preference. If this was so, it would be expected that tb would have increased correspondingly in the former British colonies. All in all, it is difficult to assess the strength of human preference. In fact, it may not be very strong and possibly erratic. The W mutant illustrates the case where human preference cannot prevail against adverse effects of a gene. The W allele produces an all-white phenotype which many people admire. Yet, although the allele occurs in most regions of the world, it occurs at a frequency of only a few percent. The reason appears to be that the allele confers deafness and lowered viability upon its recipients.

The two colour mutants which display geographical restrictions are Siamese (c s ) and Abyssinian (T a ). The former occurs in South-east Asia and probably generally in that region but is either unknown or exists at a very low frequency elsewhere. The latter occurs in South-east Asia and parts of Russia . The frequency of either mutant is not particularly high. The restricted distribution and low frequency could imply that these mutants are of relatively recent occurrence. Since the discovery of mutant alleles is a function of population size by number of generations, this could support the historical evidence that the domestic cat was thriving in the Far East long before Europe.

Two other mutants which excite interest and occur at low frequency are Manx anury (M) and polydactyl (Pd). It is easy to understand why M will never attain a high frequency because the homozygote is a pre-natal lethal and the heterozygote suffers mortality from a variety of skeletal and soft tissue abnormalities. Why Pd has not increased is not apparent for polydactous cats are not obviously handicapped nor defective although no serious studies have been performed on these aspects. Perhaps the interest is not translated into active preferences.

Until recently, all of the analyses of cat populations have concentrated upon the inter-sample frequencies of individual alleles. However, it is advantageous to study the whole array of allelic frequencies between samples - the genetic profile as it has been termed. Individual alleles may change in a given environment but the movement of populations involves all of the alleles. A recent study has considered the cats of cities in central, southern and eastern USSR , and has revealed that the southern and eastern populations are more similar than those of central provinces . This is taken to indicate that the domestic cat travelled eastwards from the Middle East as far as China before making any significant inroads northwards. In other words, the cat was following civilisation of a certain level of culture or prosperity and did not spread outwards until the social infrastructure permitted it. Admittedly, this conclusion is prompted by the concepts of earlier paragraphs but the data is not in conflict with these.

The tabby domestic cat found in Britain and Europe is more sombre coloured, is somewhat more clearly striped and has a more stocky body conformation than the more lissom lybica . Indeed, the phenotype more closely resembles silvestris . Two reasons may be advanced for this. Transporting the cat to Europe meant a sharp change of environment, for which a silvestris type cat is more suited. It is conceivable that the domestics would mate with wild silvestris , thus introducing a trickle of silvestris genes. However, the hybrids would doubtless show various degrees of wildness and most would become feral, if not eventually indistinguishable from wild silvestris . Two two processes could be complementary, of course, with the former being the more important. It may be noted that most cat populations are variable for body conformation, ranging from compactly built animals to those of a more sinuous nature. This implies persisting variability for body type.

Domestic breeds of cats fall into two distinct classes, British, European or American (according to country), which are of stocky conformation, and foreign, which are of sinuous form. This is an exaggerated reflection of the difference noted above. The concept of breeds in the cat dates from the middle of the nineteenth century (notably in Britain ) at which time names and standards of excellence were adopted. The early breeders adapted such material to hand, choosing the most likely specimens of the basic phenotypes. Such 'native' breeds were of the cold climate compact conformation. About this time, the Siamese were imported and the colour and sleek conformation caused a sensation. Henceforth, all 'foreign' or non-native breeds had to be of the sinuous form.