“THE STUDY OF THE EVOLUTION OF THE CAT FAMILY INVOLVES MORE THAN THE CONSIDERATION OF DARWIN’S THEORY OF NATURAL SELECTION”
When one first decides to examine evolution, it is Darwin’s Theory, which is usually the starting point. Most people who have received some form of secondary school education have heard of Darwin and he is generally considered to be the “Father of Evolution”. His name is known all over the world, with several places named after him. His picture has appeared on money and stamps, his portrait appears in numerous books and statues grace prominent places in towns and cities in countries worldwide. Darwin’s Theory of “Survival of the Fittest” is taught in schools and certainly goes a long way in the explanation of how animals and planted have developed over many generations. However, this is not the full picture and there are lots of other factors that must also be examined. Some of these have little or no technical backup, others have been scientifically proved, and the aim of this article is to consider the various options one by one to see why the study of the evolution of the cat family involves more than the consideration of Darwin’s theory of natural selection.
WHAT IS EVOLUTION?
The dictionary definition of evolution is “a gradual change or development especially to a more complex form”. However, biologists would tend to go into a little more detail, producing a theory that proposes that all living things are ultimately derived from a single common ancestor. Differences that are apparent between organisms are the result of a slow gradual process of accumulation of slight changes from an original form (known as the common ancestor). Similarities between organisms can be explained by their common ancestry - the more similar two organisms are, the more recently they share a common ancestor.
Classification means to systematically place things in categories. Before we can evaluate the factors involved in evolution, we must first look at classification. Man loves to classify things around him - that is why we have partitions in the cutlery drawer for knives, forks and spoons, its just in our nature to want to have a name and place for everything we find around us. This is not a recent development in mankind – the famous Greek philosopher, Aristotle, born in 384 BC, wrote a great deal about animals, classifying them by separating them into groups according to their similarities and differences. He organised them in a series of ten books (although the last was not written by him), known as “The History of Animals”. This was his longest series of writings and included sections on their external and internal features, reproduction, habitats, diseases and relationships with other species.
Over two thousand years later, in 1707, Carl Linneaus was born in Sweden. Known as “the father of taxonomy” he was a pioneer of the modern classification system. He developed a deep interest in botany and studied medicine, both in his homeland and in The Netherlands, where he published his first edition of Systema Naturae, a classification of living things. Taxonomy is the area of biology, which deals with the classification of species based on their evolutionary history. It enables us to identify living things according to their biological characteristics and trace the descent of a group of similar modern species from a common ancestor. Prior to the introduction of Linneaus’ system, the whole structure of naming species was very complex and confusing, often several words long, and different biologists would use an assortment of words to mean the same thing.
HOW DOES THE MODERN CLASSIFICATION SYSTEM WORK?
All living things are initially placed in one of five categories, known as Kingdoms – bacteria, single-celled creatures, fungi, plants and animals. Kingdoms are subsequently split into smaller and smaller groups, until they finally reach the smallest group that contains only one species, e.g.
Kingdom Phylum Class Order Family Genus Species
The group beneath a kingdom is known as a phylum, which is quite simply a group of organisms that share a few basic characteristics, e.g. Chordata, so named because all animals within this group have a long flexible rod-like structure, present when the animal is in the embryo form. Phyla are split into smaller groups called Classes; the Mammal is an example of a Class. Orders are sub-groups of Classes and creatures can belong to more than one Order. Members of the cat family belong to both Placentalia (mammals with placentas) and Carnivora (eats flesh, and have large teeth). There are also Sub-Orders, such as Fissipedia (land living carnivores). Orders are split into smaller groups known as Families. By the time a living thing is identified as being part of a Family, it will have a number of similarities to other members of the group. In the Order Carnivora, there are eleven Families, including Felidae, which contains cat-like creatures. There are thirty-eight species, including the domestic cat, belonging to the Felidae group.
Families are split into smaller groups known each one known as a Genus. The Genus is the last group within the classification system and by this stage of classification, organisms within a genus have many similarities in their physical appearance with few variations. The final stage of classification is the species, which is the basic unit.
To help in the identification of a particular species, Linneaus introduced a two-word system, known as a binomal system of nomenclature, where each species is assigned a two word Latin name and the first name is always the Genus name. Domestic cats belong to the Genus “Felis”, the small cats group, and large cats belong to the Genus “Panthera”. The one exception to this is the Cheetah, which belongs to a group on its own, because of differences between this species and small and large cats. The full systematic binomal name for the domestic cat is Felis domesticus.
Whilst modifications to the original system have been made, Linnaeus’ classification system is still used as the basis for all classification. This naming system is used worldwide and whilst classification above the species level is rather subjective, and there is no “correct” classification or universal agreement, a system of classification does enable people to discuss new discoveries. Therefore, we can track the identification, development and evolution of a specific organism. A universal system enables everyone to discuss evolution and development using a single system, not matter what country they come from or language they speak.
WHAT IS A SPECIES?
As mentioned previously, a species is the basic unit of classification and all individuals within a species have many similarities. Members of a species breed successfully to produce fertile offspring. Within a species, there may be variation in colour, pattern or even size and shape (The Great Dane and Yorkshire Terrier are both species of dog but different breeds, and whilst natural mating between these two would be difficult if not impossible, due to the size differences, in theory they could produce live, fertile offspring).
A sub-species is a group of individuals, which are the product of matings between two closely related species producing hybrids. Felis domesticus, the domestic cat, is believed to have evolved from matings between Felis lybica and Felis silvestris, known as the Felis lybica silvestris complex.
Individuals of any particular species usually live in the same basic area for many reasons but primarily to enable breeding to take place. A group of individuals belonging to a species living in the same basic area at the same time is known as a population. Over a period of time, populations evolve due to a variety of changes. However, individuals do not change.
THEORIES OF EVOLUTION
Over the centuries, there have been a number of theories of evolution put forward. Some are more realistic than others, and have been refined as man’s knowledge of both his environment and genetics have been discovered.
1. Special Creation
This theory claims that a God or Gods created every organism and placed each one on our planet as part of a master plan. However, this type of theory requires supernatural powers and cannot really be considered a science. The special creation theory is dependant entirely on faith, and has no scientific backup.
2. Spontaneous Generation
Unlike “Special Creation”, spontaneous generation does have some scientific explanation. This theory claims that new life forms spontaneously appear from existing matter. Rats would spontaneously appear out of rubbish and waste, and maggots would spontaneously appear from rotting meat. This would all happen without any obvious contribution by parents. This theory was tested by Louis Pasteur, and after careful observation and experimentation, was found to be false.
3. Descent With Modification
By the early nineteen century, many fossils had been discovered and their characteristics analysed. From this work, various points emerged –
• certain organisms had become extinct,
• Other organisms currently in existence were not present in the fossil records indicating that they had not always existed,
• And finally, the organisms that currently existed were more similar to recent fossils found near the surface than to older fossils found buried deeper down in the earth.
From the work with fossils, new ideas were put forward, namely evolution, as we know it.
Jean Baptiste Lamarck’s theory of evolution was issued in 1809. Known as “Descent with Modification”, he believed that individuals acquire physical changes through hard work, and these changes could be inherited. One example he used was the giraffe, claiming that the neck became longer because the animal had to reach for high branches. Their offspring would have longer necks as a result of this action. He also felt that a blacksmith would build large muscles though working hard, and again this would be passed onto his children.
There have been many tests based on this theory, but in actual fact, all have failed, and we now know that there is no genetic basis for inheritance of this type of acquired characteristic – not every top shot-putter will produce sons with the same heavy muscular build.
4. Darwin’s Theory of Evolution
Fifty years after Lamarck’s Theory, in 1859, Darwin published his explanation for evolution, based on natural selection, and today it is still considered the most reasonable explanation. Charles Darwin is generally known as “The Father of Evolution”. He was born in 1809, the year when Lamarck’s Theory was first presented. He initially tried to follow in his father’s footsteps commencing studies in medicine, but didn’t enjoy it so decided to study theology instead. He wasn’t really interested in this subject either, but during his studies, met botany professor, The Rev. John Henslow, who became his mentor and encouraged him to take an unpaid position as expedition naturalist and gentlemen's companion to Capt. Robert Fitzroy, on the HMS Beagle. Although the expedition was supposed to last three years, the voyage actually took five years, enabling Darwin to study plants and animals along the coastline of South America.
On his return, he studied various aspects of science and began to develop his theory. This included the idea that the offspring inherit improvements from their parents, improving with the generations. This was to prove unpopular with die-hard Victorian Christians who believed in Special Creation. Reluctant to publish his work, believing that he still had more research to do, it was a parcel from a young researcher working in Indonesia, which finally pushed him into making his work public. Inside the package was an article written by the young English naturalist, Alfred Russell Wallace. This was a theory of evolution by natural selection, very similar to his own, and seeing this work, Darwin’s friends encouraged him to submit his work. The two pieces were read simultaneously at the Linnean Society in 1858, and Darwin’s work was published as “The Origin of Species” in 1859. Whilst both men are credited with developing this theory, Darwin is considered the first, since his work was documented while Wallace was still a teenager.
Natural Selection is based on survival of the fittest, where the plants and animals that are most successful at securing food and resources are the most likely to survive and reproduce. Within a population, there will be variations between individuals.
If we look at one of the North-Eastern States of America, Maine, we can use one of the domestic cat breeds, the Maine Coon, as an example of Darwin’s theory. In a Maine climate, the winters are very cold; often well below zero in temperature. The summers in contrast can be very warm.
Predators include bobcats, capable of killing a cat, and the terrain is very green with lots of trees and undergrowth. Food would be smaller mammals such as rats, mice and rabbits. If a group of various domestic cats were released in this type of environment and left to fend for themselves, some would not manage to do so, and would consequently die out. Cats with very short, sleek coats would find it very difficult to keep warm during the winter and would probably die of hypothermia. A longhaired cat with lots of thick downy undercoat would likely become tangled in the undergrowth, and either dies of starvation or killed by a hungry bobcat. The cats would need a long silky coat to survive. The domestic cats would need a long powerful muscular body to cover ground quickly to catch their prey and a strong jaw to kill it. Cats with mouth problems, such as twisted jaws, would soon die.
Thus over many years, the interaction between the environment and individuals would determine which genetic variations would be represented in the future generations. Over a period of time, favourable inherited characteristics would appear in higher and higher frequencies and the species will change.
This theory has been proved scientifically by using artificial selection, where man chooses which two individuals will reproduce to make successful contributions to the next generation. Artificial selection has been used to produce dairy cows which produce large quantities of milk, varieties of domestic cats, sheepdogs with good herding abilities and even the members of the Cole family of vegetables, e.g. cauliflower, broccoli, brussel sprouts, kohlrabi, cabbage and collards. These vegetables are all derived from a single common ancestor related to wild mustard.
One very well documented example of natural selection is the peppered moth, which comes in two colours – peppered and black. On normal tree trunks, which are green/brown in colour, the peppered variety survived well, and the black ones were easily seen and eaten by birds. However, during the 1800’s during the industrial revolution, coal-fired factories produced huge levels of black sooty carbon, which stuck to trees, turning the trunks very dark, making the peppered moth very easy to see and therefore far more likely to be eaten by birds. The black moths were more difficult to see in this type of environment and their numbers increased dramatically, until by the early 1900’s only one percent of the moth population was peppered. As coal-fired factories have decreased as man has become more aware of the need for less air pollution, the number of peppered moths has again increased as the tree trunks reverted back towards the green/brown colouration.
It should be stressed that while natural selection does act upon individuals, it is the population that evolves. Ultimately, this evolution will produce a new species.
Scientific support for this theory comes from various sources, including comparing anatomies, molecular biology and examining embryos. It is interesting to note that all vertebrates (animals with backbones), including the cat and the human, have gill pouches and a tail at some stage during embryonic development.
When the various theories are compared, it is the theory of Natural Selection (survival of the fittest), which is considered the most likely explanation.
However, Darwin’s theory of survival of the fittest is not the end of the story. There are a number of other influences that must also be considered, since they have also have a role to play in evolution.
a) Variation, Mutation and Hereditability of Variation
Whilst all individuals belonging to a particular species are very similar in their characteristics, each one is very slightly different. These differences are collectively known as variations. No two individuals are identical in every respect, even twins which are from the same egg have some differences, albeit very tiny ones. Variations are present in all individuals belonging to a population.
The word “Mutation” automatically conjures up horrid images in many people’s minds. Thoughts of creatures with two heads or severely disfigured are commonplace when mutation is mentioned. But, many people are blissfully unaware that mutations actually occur all the time in every cell in our bodies. DNA is a massive chemical information database which carries all the information required to make any protein a cell will ever need. Because DNA has the ability to recognise and repair mistakes in cells before they are passed on to descendents, cell mutations usually have no effect. However, in some cases mutations can be passed on to offspring through the parent’s genes, and whilst some of these can cause problems, many more actually have a positive effect on the progeny. Mutations are responsible for changes to a species, from coat colour to body shape and ear size. Since data leads us to believe that domestic cats came from the African Wildcat and European Wildcat, both of which exhibit a short agouti coat, mutations over many generations to enable the cat to live in varied environments resulted in the wide diversity of coat colours, lengths and patterns we see today.
There are some mutations that do not have a positive effect, and one of these is the Manx Gene. This is believed to be a spontaneous mutation, which occurred on the Isle of Man several hundred years ago. The Manx cat has no tail and a shortened spine, which can cause a variety of problems including bowel and bladder dysfunction and difficulties in walking. It is also a dominant gene, which means that when a Manx cat is mated to any other cat, the Manx gene (M) will be exhibited to some degree. Added to this, the Manx gene is also lethal, and when both parents give M, the offspring (MM) will die before it is born. For this reason, Manx breeders do not mate two tailless Manx cats together. Had the Manx cat been a new breed today, it would never have been accepted by the cat fancy. However, its historical background allows it to continue to be accepted, although the number of breeders actively working with Manx cats is low, and it is rare to see one on the show bench.
Whilst some variations are not passed on to the offspring through the parents’ genes, others are, and when this happens, it is known as “Hereditability of Variation”. Many aspects of variation are due to these genetic differences, which pass from one generation to the next. If these variations are passed to enough offspring and their future generations, the species will eventually change. However, if the inherited variation has a negative aspect, resulting in problems in survival, then organisms expressing this variation will eventually die out if left to fend for themselves.
b) Unlimited Biotic Potential
Every species has the ability to produce far more offspring than can actually survive and this is known as “unlimited biotic potential”. Domestic cats usually start to reproduce by the time they are a year old, although many can produce at six to eight months old. A cat can go on producing kittens for a number of years, some cats will still produce kittens when they are over ten years old. If a feral cat has two to three litters each year, this would mean (if it had four kittens in every litter) it could produce a hundred and twenty kittens in its lifetime. Now let’s look at the cat’s offspring…
i. the first generation would produce 2 female kittens
ii. the second generation would produce 4 female kittens
iii. the third generation would produce 8 female kittens
iv. until the sixth generation, which would produce 64 female kittens.
If we then multiply the number in the sixth generation (64) by the number of female kittens produced in it’s lifetime (120/2), we find that in six generations, this one female cat has been responsible for three thousand, eight hundred and forty female offspring, and over seven thousand six hundred kittens in total!
Having this knowledge makes one realise why domestic cats should be neutered if not specifically acquired for breeding (e.g. pedigree cats). It also helps us to understand the potential difficulties with feral colonies, and why some charities spend time and money neutering cats within these colonies.
In reality, however, not every offspring will actually survive and whilst unlimited biotic potential is known and understood, there are other factors which prevents it actually happening. The following also influence the number of individuals, which will survive long enough to produce offspring.
c) Limited Resources
In any environment, there is only a limited amount of resources, such as food, water and shelter. Therefore, in practice, no organism can successfully reproduce to its full biotic potential. Some of the offspring will die before they can reproduce, others will not have had enough suitable nutrition to enable them to reproduce and some will never survive beyond development in the seed, egg or uterus.
All the different organisms that are found in a common environment will compete for those limited resources. Whilst they may not require the same food, the food chain can only cope with a limited level of organisms. All food chains start with the sun, which produces energy for plants to photosynthesise.
Sun Plant Herbivore Carnivore
e.g Sun Wheat Mouse Cat
In certain areas, resources may be bountiful with lots of water and food, so individual number are high, but in others where there is less water, shelter and food, not every individual will gain enough to survive and there is competition for these resources. In plants, where there are too many growing in a small area, they compete for water, nutrients from the soil and sunlight. Those plants, which do not obtain all three necessities, will die. In animals, in addition to them being unable to find enough food and starving to death, competition can even be violent, with them fighting over the same sleeping area, or food. This can lead to creatures gaining severe infected wounds, another potential cause of death.
The area in which individuals live has a huge influence on their survival and individual species have developed over generations to blend in with their particular habitat. This happens over generations, using the hereditability of variation theory. For instance, polar bears have developed a thick white coat for living in the snow.
Many members of the cat family have stripes or spots to enable them to hunt unseen in jungles or desert lands. The Sand Cat, Felis margarita, (found in areas from the Sahara though the Middle East to Turkestan) has pale sand or grey coloured dense soft fur for camouflage, very large ears to help them listen for their prey
beneath the sand (they are predominantly digging cats, eating gerbils), and their feet are covered in thick layers of wiry black hair which insulates the delicate footpads against the heat and cold in the desert. This wiry hair allows them to walk on sand without sinking in and leaves their footprints almost invisible. It is interesting to note that in captivity, they have lived up to thirteen years, but have a high juvenile mortality rate of 41%. However, as you can see by the photos, this small cat has evolved very well to survive well in its desert habitat.
f) Geographical Isolation
Geographical isolation is where individuals belonging to a species are cut off within a certain area and will in-breed between themselves. Two very well documented examples of this are Huntingdon’s Chorea in humans and The Manx Gene in domestic cats. Both are carried from one generation to the next through the parents’ genes and equally, both can be lethal. Both are believed to have happened though mutation, as discussed in section (a).
In areas with large gene pools, these genes would probably have died out over a number of generations, or at least have become extremely rare, but in areas where there was a limited gene pool, there would have been a considerable amount of inbreeding, enabling the individuals carrying these genes to proliferate.
The number of cats on the Isle of Man would initially have been small, and if just one cat had developed the mutation, then produced offspring, these related cats would then go on to mate between themselves, producing offspring which exhibited the tailless cats we know today as The Manx Cat. These cats were prized and eventually sent all over the world because of their unique lack of tail, rather than despite it.
Similarly in a small group of islands known as The Florida Keys, forming an isolated area in Southern Florida, a group of domestic cats exhibiting extra toes (known as polydactyl) evolved, probably from just one or two individuals, on the estate of the famous writer, Ernest Hemingway.
In the same way, an isolated area in East Anglia has been identified as the place from which Huntingdon’s Chorea emerged. People in this remote region would have married cousins, uncles and aunts, or nieces and nephews, increasing the chances of producing children who carried this devastating hereditary condition. Those carrying it will eventually go on to develop nerve degeneration, depression, dementia and eventually death in every case. Unfortunately, this condition does not express itself until the individual is normally over thirty years old, by which time many will have actually produced children themselves, thereby passing it on to a percentage of their offspring. Although initially it was restricted to a very small area of England, as transport improved and people began to move around more readily, some of whom left Britain for a better life in the new world, they unintentionally took the disease with them, and it can now be found in most areas where Western Europeans have settled. Thankfully, there is now a genetic test available to determine whether an individual carries Huntingdon’s.
Geographical isolation can have a major effect on populations within an environment, instrumental in producing key changes to their characteristics. In some cases, it can be positive, producing organisms that will blend into the environment, but in other cases it can have devastating results, producing individuals with hereditary diseases, which affect their ability to survive.
A hybrid is an animal or plant resulting from the cross mating between two different biological species belonging to the same genus. Hybrids exhibit characteristics of both parents, sometimes making them appear as if they have been sewn together. Both plants and animals have the ability to form hybrids. Many flowers and vegetables we have today are the result of man-made hybrids, bred specifically to be taller, prettier or produce more fruit. Animal hybrids are also seen, both in the wild and in captivity, however, many of them have fertility problems. Some are infertile from being born; others have limited fertility, which diminishes, as they get older. The level of fertility depends on how closely related the two species are. The mule is the result of a mating between a male donkey and a female horse. Whilst this hybrid is found all over the world, used in farm work and a means of transportation, it is always infertile, proving that the horse and donkey are not very closely related. Some of the big cats, lions and tigers for example, have been inter-bred, and offspring have been produced, but again, these have been infertile.
Some of the smaller cats, including The Bobcat, Geoffrey’s Cat and Little Spotted Cat, have been mated with domestic cats, although the offspring’s level of fertility has not been well documented. However, one hybrid mating has been well reported, that of the hybrids produced between the Asian Leopard Cat and the domestic cat, since this has been used to produce a new breed of domestic cat, The Bengal. We will look at this hybrid in more detail later.
From work carried out, it has emerged that the more closely related two species are, the more likely they are to produce fertile offspring when mated together. This information has enabled us to determine possible ancestors of the domestic cat, since Felis domesticus and Felis chaus have produced fertile offspring, as have matings between Felis lybica, Felis Silvestris and Felis domesticus. In fact, the European Wildcat in Scotland (Felis silvestris) is in danger because of its ability to interbreed with domestic cats. It is thought that a number of Scottish wildcats in their wild existence are now hybrids rather than pure Felis silvestris.
However, one cannot assume that something is a hybrid purely on looks alone. There are breeds of domestic cat which resemble other species of wild cat, the Ocecat for example with is beautifully spotted coat could make people assume that it comes from one of the small wildcats. The Maine Coon was believed to have evolved from matings between domestic cats and racoons, although matings have now proved this not to be the case, since no offspring were ever produced. Only test matings can really prove whether certain individuals are from two closely related species.
If two closely related species produce enough hybrids, then eventually there will be enough individual hybrids to form a new sub-species.
The African Wildcat, Felis lybica, was a relatively tame species, known to have lived alongside the Egyptians, later to be taken all over Europe by Romans and worldwide by seafarers. On arrival in Northern Europe, it is possible that some of these cats were left behind and they mated with the
larger European Wildcat, Felis silvestris, known to have an inherent fear of man. However these two species could have produced a sub-species, Felis silvestris-lybica complex, combining the tame gene from the African Wildcat and the wild gene from the European Wildcat, eventually over a period of generations evolving into a tame cat which resembled both species, eventually developing into what we now know as the domestic cat.
h) Human Influences
Man, as a single species, have had more effect on our planet than any other factor, and no matter how forward thinking the early evolutionists were, they could never have foreseen what humans have done to the world around them. In recent years, man has become more aware of the environment around him and made efforts to help prevent further destruction, but for many, many years this was not the case and many species became extinct through man’s interference. However, it must be stated that in many areas of the world, devastation still continues and the number of species with which we share our world, continues to decrease by the year.
Man has intervened in nature for thousands of years, and by this he has affected its natural course. For thousands of years he has hunted other animals, believing that their numbers would be unaffected by what they did. Sadly, this is not true, and even though hunting endangered species is now severely frowned upon, there are those for whom the possibility of large amounts of money are a great temptation, particularly if they are living in poverty.
Man influenced the spread of the small cat, domesticating certain species, probably predominantly Felis lybica, which eventually resulted in the domestic cat, and by taking it around the world with him, he succeeded in helping it to populate the entire planet, with the exception of a few small isolated areas. Whilst I feel that the majority of people have no problem with this, some of Australia’s native creatures and in other isolated places such as Mauritius, (where several species of native bird have almost become extinct due to the domestic cat’s successful hunting prowess), have been affected by its introduction.
Man has also cut down rain forests, re-developed long-standing marsh-lands, ploughed out hedgerows, altered long-standing eco-systems, and even in some cases, destroyed them completely, killing the only habitat in which certain species can survive, all to improve production levels or places for humans to live. In recent years there has been movement to protect endangered species, and many are now involved in breeding programmes in captivity, with the aim of preventing total extinction.
In a smaller way, man has helped to develop new breeds within a species and even to ensure that they survive. Three examples are found within the domestic cat – The Bengal Cat, The Sphynx and The Manx Cat, all of which can have potential problems. Without the intervention of man, none of these breeds would have become household names, as they are today.
Considering all the various possible influences on evolution, it is the influence of a single species, man, which has probably had more effect on the world and its development than any other factor.
APPLICATION TO THE EVOLUTION OF THE CAT FAMILY
Having now examined a number of factors that affect evolution, we can now apply this information to the cat family.
The cat family (Felidae) is split into three genera – Felis, Panthera and Acinonyx.
Cats belonging to the Felis group, known as the small cats, all have a small chain of bones, known as the hyoid, which connect the larynx to the skull. This makes the structure rigid, preventing them from being able to roar. Most cats belong to this group. Some taxonomists have given members of the Lynx group their own sub-genus, Lynx.
Members of the Panthera group, known as the big cats, all roar, due to some of the small bones in the hyoid being replaced by cartilage. Cats belonging to this group include the Lion, Tiger, Jaguar and Leopard. However, the Puma (Felis concolor) does not belong to this group, despite its size. It is actually the largest member of the small cat family.
The final group, Acinonyx, has just one species, the Cheetah (Acinonyx jubatus).
The modern Cheetah is the last of four species that lived during the Pleistocene era (2 million to 10,000 years ago). Through confusion, the Cheetah is thought by some to belong to the big cat family. However, it has certain differences, which place it in a group of its own, predominantly the fact that it does not have fully retractable claws.
No two cats are identical, even if they belong to the same species. If you were to look closely at two lion, even littermates, then there would be visible differences, perhaps the length of tail or colour of the coat may show minute differences. Some of these differences are due to mutations within the individual’s cells, other have been inherited from one or both of the parents. These differences can lead to one individual surviving and another dying. Sometimes, albino animals are born. These lack the coloured pigmentation, producing a totally white creature, often with pink eyes. In the cat world, some cats exhibit partial albino, having a white coat with blue eyes. Some even have partial markings - an example of this is the White Tiger. However, white cats of all species can have problems caused by the sun burning their delicate pink skin, poorly protected by a white coat. This can lead to skin cancer and eventual death if left untreated. In the wild, white cats living in very hot sunny climates would not survive because of this problem. However, those living in cold, snow covered areas would blend in with the environment, enabling them to catch their prey undetected.
Many cats have some form of stripes, spots or agouti ticking to enable them to survive in a variety of environments from forests to desert. These have evolved over many generations and are cause by mutations, which have actually helped species to survive. As their environment has changed, cats which are camouflaged will be more successful hunters and less likely to be killed by larger predators, including man. The Bobcat (Felis (Lynx) rufus) has evolved to become a very successful hunter. Over many generations, this cat has developed long legs, the back ones being higher than the front to enable powerful jumping, and large round feet to give stability on rough terrain and rocks. It has a spotted and barred coat, which provides excellent camouflage in the mountains, forests and desert areas of North America where it lives.
The coat colour varies considerably, from light grey to red-brown. These changes are examples of how mutations can help a species to survive.
Mutations are the reason we now have such a wise variety of coat colours, patterns and lengths in the domestic cat.
However, not all mutations are good. Some mutations which are passed on from parent to offspring will cause problems, some of which are life threatening. The Manx Gene is an example of a mutation that produces a negative effect.
Another factor which influenced the evolution of the cat family is the hybrid, where two very closely related species of cat breed to produce fertile offspring which then go on to develop into a sub-species, such as Felis silvestris-lybica, thought to be the forefather of the domestic
cat. Not all related species will produce fertile
Matings between lions and tigers have
produced offspring, but these were found to be infertile, proving that whilst the two species are closely related, they are not close enough to produce a subs-species.
It is interesting to look at the Cheetah at this point. The Cheetah is the most primitive of the Felidae Family, evolving around 18 million years ago. It is thought that some disaster wiped out most of the cheetahs, with only a thousand or so surviving. Because they are not closely related to any other cat, there is no possibility of hybrid matings. Genetic work has found that whilst there are seven sub-species of cheetah, they are all almost genetically identical, with more similarities than humans within a family. Because they are evolved from a relatively small gene pool, they are known to be genetically fragile, and more susceptible to weaknesses and illnesses than a larger, more stable species population. This problem, combined with the fact that they are still hunted by some, either because they are considered pests to their livestock or for pure pleasure (if one could call this pleasure). The Cheetah is one of our endangered species, and without help from man, it will die out completely. News broke in October 2000 that a team from India is making plans to clone cheetahs to prevent them dying out completely. It remains to be seen whether this ambitious plan will ever happen, and what its consequences may be.
Throughout this essay, we have continued to mention the environment, the habitat in which a species lives. As the environment changes, each species must adapt in order to survive. Some develop different coat colours or patterns, other learn to eat different foods. In Egypt, the African Wildcat began to lose its fear of man, moving close to human colonies in order to feed and share shelter. In America, Norway and Russia, three breeds of the domestic cat all developed in a
similar way to cope with the particular climate and habitat in which they lived. These breeds, The Maine Coon, Norwegian Forest Cat and the lesser-known Siberian, all have long powerful muscular bodies and semi-long shaggy coats to keep out the cold. They all evolved in the same type of climate and terrain, though in different parts of the world, and are excellent examples of survival of the fittest. Those cats with short sleek coats would not survive the very cold winters. Equally, the Sand Cat (mentioned above) has evolved to survive well in dry hot desert conditions. All members of the cat family produce more offspring than they would need to if there were no dangers. However, some kittens will die before they reach sexual maturity, and the excess number is required if the species is to survive. In some species, only one or two kittens are produced in a litter, whereas in others eight or more can be produced.
And finally we look at the influence of mankind. As in every other aspect of our world, man has influenced the evolution of the cat family. He has destroyed large areas to make way for development for human use, forcing many species to move or drop in numbers. His natural instinct to hunt has resulted in a number of cat species to decline to very small numbers. This includes the well-documented Cheetah and also the less well publicised Asiatic Lion, a sub-species of the African Lion. Once widespread throughout Southwest Asia and into Europe (the Romans used to fight these big cats in arenas for entertainment), the Asiatic Lion is now found only in a single location in the wild, the Gir forest in India. In 1990, a census of these wild lions estimated that there were only about two to three hundred left in the Gir Forest. A number of zoos, including Twycross, and Chester, do keep these animals, working together to breed in captivity to prevent them from becoming extinct. It is imperative that we do not lose these proud wonderful creatures though ignorance or neglect.
However, man has also helped to introduce new sub-species and breeds within a species. His movement around the world, taking his cats with him, has ensured that almost every continent now has a domestic cat population. It is through his exploration of new areas that the African Wildcat and larger European Wildcat crossed paths and mated. As well as unintentionally helping to found this sub species Felis silvestris-lybica, man is also responsible for producing new breeds by artificial selection and hybridisation. The use of carefully selected domestic cats over a number of generations has enabled pedigree breeds to develop. A domestic cat is considered to be a pedigree if its parental background for at least three or four generations is known and documented, and it breeds “true to type” where all the kittens will resemble the breed it is supposed to be. For example, if two British Shorthairs are bred, the offspring will all have the typical British Shorthair features – they will have short plushy coats, be stocky in build with large eyes and a round head. However, if two non-pedigrees, which resemble British Shorthairs, are mated together, they could produce kittens of all shapes and sizes, depending on their background.
Certain breeds of domestic cat would not have survived at all, had it not been for human involvement. The Sphynx has virtually no coat, just a very fine layer of down over the surface of the skin. Had it been left to survive, this breed would have died out very quickly, unable to keep warm in cold weather and suffering from severe sunburn in hot weather. Whilst they are bred in the UK, the largest feline registering organisation, Governing Council of the Cat Fancy (GCCF), refuses to recognise them partially because of the potential problems when they are sold to ill-informed people who may decide to let them outside. Another breed, the Manx Cat has a history of health problems caused by the lack of tail and shortened spine. However, unlike the Sphynx, which is a relatively new breed, The Manx is registered and hold full championship status with the GCCF, since it was one of the early breeds to apply many years ago. However, if the breed was being developed today, it is highly unlikely that it would gain any recognition because of these problems. At the other extreme, the Persian Longhair would not have survived without man to take care of its profuse coat and potential eating difficulties because of the very short nose.
Some hybrid matings have been carried out between domestic cats and other closely related members of the small cat family, Felis, including the Asian Leopard Cat. Hybrid kittens from these matings have been used to develop a new breed of domestic cat, The Bengal. However, this is not without its problems. In the first Asian Leopard Cat x Domestic cross, all the males are sterile and females have limited fertility. In the second generation, the females are fertile, with males having limited fertility. It is not until the third generation that we see both sexes becoming fully fertile. There is also a question over the breed’s stability of temperament, with some cats reverting towards their wild state as they get older. Whilst this is continually being worked on by breeders involved with the Bengal, it is an area, which in my opinion, still requires much deeper evaluation, particularly when these cats are entering homes as pets. I remain concerned that in the future, the cat fancy could see a number of these ending up in rescue organisations, unable to find homes because of their temperament problems.
Thankfully, over the last century, man has taken a more active interest in the creatures with which he shares his planet, studying their movements, breeding cycles, habitats and numbers. Because of this, people are now more educated on the subject of the effect they can have on other organisms. There is now genuine concern and hunting cats is now no longer a politically correct activity. Far fewer people actually wear fur coats than they did fifty years ago, although there are still fur farms around the world. Man is now beginning to realise the mistakes of his forefathers, which resulted in the loss of so many different animals and plants, and there are many organisations that work purely to prevent this happening to many more. His attitude is slowly changing. However, there is still a long way to go before we can truly make up for all the damage we as a species have done over thousands of years. Some things have gone forever and no matter what we do, we will never be able to bring them back. We must ensure that we continue to work towards conservation and educate people to prevent more damage.
When considering the evolution of the cat family it is important to examine influences other than those put forward by Darwin.
Although other theories of evolution have been put forward, it is only Darwin’s Theory that has sound scientific backup. Fossils show that there has been life on earth for about 3.5 billion years. By examining fossils in different areas of the world and at different depths within the earth, scientists have been able to deduce that different species evolved from a common ancestor. Darwin’s Theory of Evolution was based on survival of the fittest. Therefore, animals that had adapted well to their particular environment, for example have coats that camouflaged them from their prey or predators would be successful, eating well and producing offspring. These offspring would inherit some of their parents’ traits, and if these actually had a positive effect, the species would continue to extend, provided there was not too much competition or overproduction of young.
We now have much more scientific knowledge that was available in Darwin’s time. This has enabled us to develop a much more detailed idea of evolution than the simple theory put forward by Darwin and Wallace. Whilst at the time of writing his work, Darwin had no knowledge of genetics, (this work was carried out by Mendel); his theory actually suggested that inherited traits could give individuals a better chance of survival.
In general, whilst there are a number of influences that have been considered alongside the basic “survival of the fittest” theory, in actual fact, none of them actually contradict Darwin’s original theory. They all actually serve to back up his theory, and give expansion to it rather than dispute it. The only exception to this is the influence of man, particularly in serving to protect and increase numbers in certain individuals and sub-species, which would never have survived had man not intercepted. This is particularly the case in some of the domestic cat breeds, such as the Persian, Manx, Bengal and Sphynx.
In conclusion, I believe that Darwin’s Theory was correct and scientific information gained since has just added more pieces to the jigsaw. However, the one piece that doesn’t fit, is man’s influence, where he can actually choose to destroy, or nurture and develop individuals within a species which would have no chance of survival without his help. Man has a lot to answer for in recent evolutionary history and is, in my opinion, the most important influence requiring consideration apart from Darwin’s Theory of Natural Selection, when examining the evolution of the cat family.
By: Daphne Butters