Many believe that cats are domesticated just like dogs or farm animals. But does science agree with this notion? Did cats really change so much from their wild ancestors?
Cats and humans coexisted for about 10,000 years. However, during this period of time domestic cat’s morphology, physiology, and behavior have changed very little from its wild ancestors (1, 2).
Cats, whether kept indoors or living outside, do not lose their natural instincts. Jumping to high places, scratching, burying feces, chattering teeth at birds, hiding from strangers and feeling stressed, paranoid due to changes in its environment, hunting small animals, fighting for territory etc. – all these are the expressions of the natural cat behavior.
Scientists, studying the behavior of domestic cats, agree that the domestic cat behavior is similar to that of wildcats (3, 4, 5). Due to similarities in their behavior, the findings from studies about the domestic cat behavior could be used to improve the welfare of wild cats kept in captivity (3, 5).
Does the “domestication gene” exist in cats?
Undoubtedly, friendliness and tolerance to humans give the impression that a cat is “domesticated”. But does an adaptation to living with humans really has led to the genetic changes in a domestic cat? A group of scientists think that it did: they believe they are getting closer to finding the “domestication gene” in cats, or more specifically they predict where such genes could be located (6). But it is not possible to generalize that all domestic cats possess these genetic changes since the study was performed on cat breeds only, and breeds are not representative of the cat population as a whole. Besides this, not a single wildcat included in the study was from F.l. lybica species from which all the domestic cats originated. Instead, researchers compared cat breeds to two European wildcats (F. silvestris) and two Southern African wildcats (F.l. cafra), one of which was a cat named Nancy, brought from the Arabian Peninsula (49).
While the “domestication/tameness gene” may be present in some cats, we do not know whether the majority of friendly cats possess it or if it matters more than socialization.
There is probably no single gene responsible for tame behavior. The presence of called “friendly genes” in cats may have nothing to do with human influence at all. As demonstrated by a study on rats and rabbits, the behavioral predisposition to tameness exits as a genetic variation in wild animal populations (7, 8, 46). There is no reason to think that these genes, that give an advantage to animals in adapting to an anthropogenic environment, are rare in wildcat species.
Yet, the “domestication genes” or absence of them may not be the most important factor that turns a cat into an affectionate, non-aggressive pet.
Tameness and friendliness towards humans is likely not a heritable trait – this is a learned behavior. A cat, in order to become a good pet, must be socialized at an early age (9, 10). Socialization of free-living cats in urban areas mostly happens unintentionally. Kittens that associate human interaction with positive experiences and rewards (usually related to food), tend to become affectionate adults. On the other hand, if a cat is not accustomed to humans, it exhibits wild behavior and becomes “feral”.
Although socialized cats may seek out human contact, they do not depend on humans for their survival. In general, cats are efficient hunters just like their relatives, European wildcats (11).
Because domestic cats retained their hunting skills, this worries conservationists who are concerned about the possibility that domestic cats are adversely affecting the wildlife and vulnerable ecosystems where they are introduced, non-native predators.
It is worth to note that domestic cats could have been contributed to the extinction of mammal and bird species in Australia and the United States (12, 13, 14).
Unlike the United States and Australia, cats are native/indigenous animals in Anatolia and lived there probably for a hundred thousand years or even millions of years if we include the ancestors further in the Felis family tree (32). There is no evidence that cats in Anatolia impact birds and other animals. Anthropogenic factors, such as the destruction of animal habitats, land clearing, expansion of Turkish cities and overall lack of interest in conservation, do a significant damage to the wildlife of Anatolia (15).
Phenotype and morphology: do cats have 30% smaller brains?
Charles Darwin suggested that domestic cats have slightly longer intestines than wildcats because of the adaptation to a diet that tends to include less meat (16).
This claim is not correct. The domestic cat has not evolved any metabolic adaptations like for example, dogs which developed an ability to digest starch (17). The nutritional requirements of domestic cat remain unchanged as would be expected for the carnivorous feline (18, 19). Further studies demonstrate the similarities of diets between feral cats and European wildcats (11).
While the intestine length may be helpful to distinguish the European wildcat from the domestic cat (20), we should not forget that the domestic cat did not descend from the European wildcat. The differences in intestine length are species-specific, unrelated to the effects of domestication.
Another common argument is that domestic cats have 30 % smaller brains than their wild counterparts (21). Once again the research disproves this claim: Cats have brains as would be expected for their body masses, meaning that the reduction of brain size due to domestication was not detected (22). Moreover, it was found that domestic cats and its close relatives Asian (F.l. ornata) and South African wildcats (F.l. cafra) have a similar brain size and skull morphology (48).
Big cat myth: did cats get smaller than their ancestors?
Reduction in body size seems to occur in many animals through domestication, so the researchers assume that domestic cats also got smaller compared to their ancestors. We should point out an inconsistency in this argument, which seems to be anecdotal rather than based on actual observational data. We do not have any reliable data demonstrating what exactly the domestic cat ancestor looked like some thousands of years ago, but we can still obtain some useful knowledge when comparing the domestic cat to its closest relatives. The weight of F. lybica subspecies ranges from 2 to 6.4 kilograms (Table 1), similar to that of non-obese normal domestic cat’s.
Weight and size of the cat depending on cat’s diet, age, its individual genetic makeup, and other factors. Another important thing to consider is morphological differences between sexes. Apparently, females are significantly smaller in size than males. The measurements such as body to head length and tail length seem to correlate with sex and how large the cat is (Table 1). Overweight cats also appear to look larger, so are some cat breeds selectively bred for their larger size (for example, Maine Coon).
Based on the table above (Table 1) of closest relatives of the domestic cat, the claim that domestic cats are smaller than their ancestors seems to be unfounded, therefore, offers little to the discussion of cat domestication.
Does the variety of coat colors in cats indicate their domestication?
The wildcat, from which the domestic cat originated, was a shorthaired brown mackerel tabby. This is the most ancient color of the cat (23, 24). But the domestic cat has not one but a wide range of coat color variations. So how did the other coat color phenotypes emerge and when?
Different coat color mutations occurred spontaneously from time to time in wildcats even before they had a chance to meet humans. These mutations were very rare and had no selective advantage over typical mackerel tabby phenotype, so the natural selection usually weeded them out of the population (25).
The molecular mechanisms responsible for coat color diversity are very similar or even identical in all domestic animals (25).
While coat color and other phenotype changing mutations occur by chance, human preference is not random: It is the primary driving mechanism that led to the number of fixed coat-color phenotypes observed in cats today (26). Still, though, it is the matter of the natural selection which does not disappear just because animals live in human-altered environments. No one tried intentionally tried to select cats for their coat colors.
Being different was probably an advantageous trait in human environments because humans liked cats with unique looks that stood out from the rest of shorthaired tabbies (25). We can speculate that ancient farmer communities were more tolerant to the presence of cats with different phenotypes, and some probably held superstitions and magical beliefs related to these cats. Whatever the reason was, humans increased the chances of survival of cats with these mutations by feeding and providing a protection for their offspring. The deliberate breeding, however, was out of the question. It appears that very little effort was needed if at all, to sustain the rare color mutations (47). It could be because many of coat color mutations had no negative effects on a cat’s health and survival.
Geneticists regard the coat varieties, present in nearly all modern populations of cats – the long fur (27), black, dilution (grey, cream), blotched tabby, orange/red tabby, dominant white, white spotting and probably silver – as “ancient” mutations (28). It is very difficult to tell when these mutations appeared in tame wildcats. The black color or melanism, was probably the first mutation to emerge, as it readily occurs in many wild cat species (29).
Remarkably, the mutation of the white coat has a very interesting origin. White and white spotting fur was caused by a retrovirus which inserted itself into the cat genome and was passed down to the later generations of cats (30).
Some coat colors probably have a more recent origin. Colorpoint coloration, a type of albinism, is one such an example, which occurred in Far Eastern cat populations. No matter when or where the variety of coat phenotypes occurred, it is very easy to incorporate them to the wildcat populations. Even if we believe that “wild” and “domestic” cats are distinct populations (they are not, at least not in Anatolia), even minor interbreeding between populations would result into wildcats being homozygous for coat color genes other than mackerel tabby, making them indistinguishable from the “domestic” cats (see Figure 1).
As illustrated by one comprehensive study on grey wolves, the coat color is not a reliable way to identify hybrids. Some wolves that looked like typical grey wolves were actually hybrids but wolves with an unusual, black coat color surprisingly had no detectable admixture from domestic dogs, except for one color gene (50).
Is Anatolian Cat – a wildcat?
The line between domestic cat and wildcat is blurred in the Near East because tamed (domestic) cats were never isolated from their wild siblings, F. l. lybica. The ongoing gene flow between the wild and tame cats prevented the separation of the wild and domestic lineages (31, 32, 33, 34). This would explain why domestic cats and lybica-type wildcats from the Near East, are indistinguishable from each other genetically (32, 33, 35; see figure 1). Anatolian cat and F. l. lybica appears to be the same cat. This realization has profound implications because it challenges the accepted notion that the domestic cats and F. l. lybica wildcats are the separate populations. This also forces us to rethink the methods for F. l. lybica’s conservation. Currently F. l. lybica species are not considered to be endangered (36).
There data on domestic cat ancestor, F. l. lybica, is very limited, so it is difficult to judge how much the domestic cat has changed, if at all. Most studies compare the domestic cat with the South African wildcat F. l. cafra, which is different from F. l. lybica genetically (37, 38, figure 1). Frequent mixing with wild populations as well as other wildcat species further complicates the domestication issue (39, 40).
Cat breeds – another proof of cat domestication?
Although domestic cats exhibit a variety of coat colors and patterns, cat’s physiology, morphology and behavior did not undergo any significant changes. Therefore, theoretically, it is not wrong to call the natural populations of domestic cats as wildcats Felis lybica. Taxonomists and some conservationists who classify domestic cats as separate species under name Felis catus would oppose this notion not because it is wrong or unscientific but due to unjustified fears that changing the status of the domestic cat to species of the wildcat would strip away the legal protections from other wildcats, such as European wildcat, and would make them an official target of eradication (51).
If domestic cats are actual wildcats, what about cat breeds? It is difficult to imagine a Persian cat being a wildcat. Because of its behavior and appearance, Persian appears far removed from its wild ancestors.
Some researchers think cat breeds, but not natural cat populations, could be classified as domesticated cats because of the following reasons: humans control the breeding, territory and food supply of breed cats and keep them permanently isolated from the wild populations (2, 41). In particularly, breeds like Siamese, Persians and their derivatives, have been subjected to the intensive artificial selection that resulted in extreme morphological changes.
Furthermore Persian, and its breeds (Figure 3) have distinctive behavioral traits that set them apart from the natural cats. Persian breeds are docile and less fearful towards humans. However, the distinctive behavioral traits are not due to domestication but arise from a type of genetic syndrome associated with mental retardation and development abnormalities (42).
However, some researchers generalize that unusual traits such as short muzzle (Persian breeds), floppy ears (Scottish fold), dwarfism (Munchkin), hairlessness (Sphynx), curly hair (Selkirk Rex) present in cat breeds indicate that domestic cats in general acquired so-called “domestication syndrome”. In other words, these phenotypic changes found in breeds are said to be proof that cats are domesticated (43, 44).
Such a generalization is misleading. Cat breeds with unusual mutations/disabilities, like folded ears and similar, descended from a few founders. In general, these type of mutations occur at very low frequencies in natural cat populations or have already been eliminated by natural selection. It is necessary to treat the man-made and natural cat population as separate when discussing the effects of domestication on cats. We can think about cat breeds as analogical to domesticated silver foxes from Russian breeding experiment (45), and natural cat populations as wild foxes. The mere existence of domesticated foxes does not impact the wild fox populations or make them domesticated – the same goes for cats.
Domesticated or not?
Domestic cats, especially free-living cats from Near East, retained nearly all of their ancestor’s wild characteristics and genetically they are indistinguishable from the wildcat species Felis lybica lybica, therefore we can conclude that domestic cats are rather tame than domesticated.
Cover image: Furkan Fatih Sezgin and Avi Ben-Zaken
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