Why humans don't have tails. Genetic basis for our tail-loss evolution.

Unlike our domestic cat companions we don't have tails. You've probably noticed! 😉😎 But we might have had tails and think how different the world would be if we had retained our tails like our primate cousins. The mind boggles. One's imagination can run riot with that image. All the chairs and all the sofas and all the seats on trains and buses would have to be changed.

Human with a tail in X-ray. Image by DALLE.

RELATED: Evolution of the blotched tabby pattern of domestic cats.

So what happened? Well, firstly, unlike Tucker Carlson, you've got to believe in evolution to believe in this scientific explanation. In fact, I hope Carlson reads this article because it might make him see sense about evolution. He believes that God created humans and animals under the creationist theory. He says there is no evidence for evolution which is wrong but he believes creationism about which there is certainly no evidence whatsoever. Tucker Carlson is irrational.

"It has long been speculated that tail loss in hominoids contributed to orthograde and bipedal locomotion, the evolutionary occurrence of which coincided with the loss of the tail" - quote from the study - see citation at base of page.

The reason

In summary, a genetic parasite altered a crucial gene related to tail development when our lineage diverged from other primates around 25 million years ago. This alteration ultimately led to the disappearance of tails in apes, including humans. Our tailless state owes its existence to this ancient genetic twist.

In some more detail: over millions of years, DNA undergoes changes that drive evolution. One intriguing element is the Alu element, a repetitive DNA sequence found exclusively in primates. These “jumping genes” can insert themselves randomly into the genome, potentially disrupting or enhancing gene function. In this case, the Alu elements reside in the TBXT gene, specifically within introns (DNA sequences flanking exons). Introns were once considered the “dark matter” of the genome, assumed to serve no purpose. However, when cells use the TBXT gene to generate RNA, the repetitive nature of Alu sequences causes them to bind together.

The researchers discovered two Alu elements in the TBXT gene, present in great apes but absent in monkeys. Remarkably, these elements reside in introns, not in the protein-coding exons. When RNA molecules are generated from the TBXT gene, the Alu sequences bind together, potentially influencing tail development.

Now, that is highly technical and I don't fully understand it but that is the current explanation as to why humans don't have tails. You can boil it down to the way evolution works and the way genetic mutations sometimes arise during evolution which leads to the creation of a different kind of animal and that animal does very well in terms of survival and therefore this alteration to the appearance and physiology sticks around and doesn't disappear.

Bo Xia, is the first author of the study (formerly a graduate student at New York University and now a principal investigator at the Broad Institute).

RELATED ARTICLE: Feline Evolution in Brief.

Study Citation

Xia, B., Zhang, W., Zhao, G. et al. On the genetic basis of tail-loss evolution in humans and apes. Nature 626, 1042–1048 (2024). https://doi.org/10.1038/s41586-024-07095-8

P.S. please forgive the occasional typo. These articles are written at breakneck speed using Dragon Dictate. I have to prepare them in around 20 mins.

Why does the dominant white gene cause deafness in some cats?

The dominant white gene in cats is associated with an increased risk of deafness. This is because the gene affects the development of the cells in the inner ear that are responsible for hearing.

All-white semi-feral cat. Image in public domain.

The dominant white gene can cause the cells in the inner ear to fail to develop normally, leading to a condition called congenital sensorineural deafness. This type of deafness is caused by damage to the hair cells in the inner ear, which are responsible for converting sound waves into electrical signals that are sent to the brain.

RELATED: What percentage of white cats are deaf?

Cats that have one or two copies of the dominant white gene are at an increased risk of developing congenital deafness. This is particularly common in cats with white fur and blue eyes, as the gene that causes blue eyes is closely linked to the dominant white gene.

RELATED: Deafness in cats – causes, diagnosis and management plus dog info. too

It is important to note that not all cats with the dominant white gene will be deaf, and not all deaf cats have the dominant white gene. Deafness can also be caused by other genetic mutations, environmental factors, or as a result of age-related hearing loss.

'Agouti'. What does it mean?

You see the word "agouti" use quite a lot by the cat fancy and on cat websites. What does it mean? It's a reference to a type of coat which we know very well, a tabby coat. Specifically, it refers to the genetics of a tabby coat. Agouti is the name given to a coat in which each individual hair strand is pigmented with bands of black, brown and yellow.

The most typical agouti pattern is seen in the ticked tabby coat of the Abyssinian cat; an "all-agouti" cat. The classic tabby cat that we see has blotches of dark areas and so we have, in the words of Robinson's Genetics, a tabby pattern which "consists of two coexisting systems of pigmentation or, more likely, a background of agouti, with a superimposed system of stronger black pigmentation."

The background of agouti as they state are areas in which the hair fibres are banded or ticked with alternating black or yellow pigmentation as mentioned.

Superimposed on this are areas in which almost all-black hairs predominate in which the yellow band is reduced to the very base of the hairs.

If you look closely at a tabby cat at each individual hair strand, and if you follow the black areas i.e. the markings, you can see that the top of the hair strand is black whereas going down the hair strand towards the skin you can see light yellow.

My tabby cat. He has a spotted tabby coat. Very wild cat looking.

It is the way these particular hairs are placed on the coat which provides the markings that we see which in addition to the blotch tabby mentioned, there is the spotted tabby and the striped or mackerel tabby.

The cat's genetics dictate the location of these hair strands that provide the markings.

The agouti coat is the original wild-type colouration by which I mean it is the coat of the wild cat ancestor of the domestic cat and other wild cat species.

Study on pet wolf behaviour helps explain why wild cats don't make great pets

It is my contention that true wild cats like the serval don't make good pets because they are not backed up by 10,000 years of domestication. I believe that memory can be inherited. It is called genetic memory. This is why young offspring of wild animals such as wild cats or wild dogs immediately know how to do things completely instinctively. And it's why domestic cats have the memory of human behavior in their DNA.

Zena, a pet serval, and James Brown's partner? Photo: James Brown.

And I believe that domestic cats over thousands of years of domestication learn how to interact with people and that this memory is held in their genes to be passed on to their offspring. And the study on young wolves regarded as pets to their owners found that they could never quite pick up inferences from human behaviour as could domestic dogs. Therefore, they were unable to communicate with people in quite the same way.

Dogs are born with an innate ability to understand what humans want to communicate to them. Their ability is to read people because of perhaps 20,000 years of domestication. Dogs have been domesticated for far longer than cats because they were and still are working animals.

Because they understand people better, they form much better bonds with people than do pet wild dogs i.e. wolves. Across a range of tests in the study the dog puppies greatly outperformed their wolf cousins. For example, despite puppies, only a few weeks old, know where to find their food because the human is pointing at it whereas not one of the young wolves in the study did any better than chance. In other words, there was no background, inherited skills.

The pet wolf is a raw product without a history of interacting with human beings. Take that from the study and you get the same effect in living with exotic cats as they are called, which refers normally to the small and medium-sized wild cat species such as the serval, as mentioned, and sometimes the cheetah or even the mountain lion. I have seen people regard mountain lions as pets. They even go a step further and have lions and tigers as pets sometimes but the relationship between cat and person will never be the same as with a domestic cat.

Wild cats as pets are not able to create the same bond and understanding between themselves and their human carer as the humble domestic cat. That is not to say that bonds are formed. Some people say that exotic cats such as the F1 Savannah create strong bonds but that cat is half domestic cat.

P.S. The study referred to was carried out at the Wildlife Science Center in Stacy, Minnesota and published in the journal Current Biology.

Fedya, the cat with a permanently startled face and chunky cheeks

Fedya lives in Rostov, Russia with his human caretaker Natalia Zhdanova, 40. She found him as a poorly stray kitten in her garden, took him in and nursed him to good health with the help of her neighbour's cat, Handsome, who looked after Fedya, nursed him and licked him and now they are the best of friends.

Startled Fedya. It's permanent and he isn't startled! Photo: his Instagram page.

The point of this short post is that Fedya has a permanently startled expression which is a nice change from a permanently grumpy expression. Grumpy Cat started off the grumpy cat look and there were one or two after her who did very well on social media.

What I noticed about Fedya is that he looks like a male cat who has not been neutered with his chubby cheeks. This is a typical non-sterilized male cat look. I don't know whether he has been sterilised but except for his started appearance he looks like a fully intact male, blue British Shorthair, which he isn't because he was a stray cat in Russia. His coat is definitely a classic blue (grey in non-cat fancy parlance).

When she found him, she said that he was "very weak and was dying". He turned into a very playful, intelligent, sweet and gentle individual who purrs very loudly and who is inseparable from Handsome. As expected, he has an Instagram page which I can't find but he's gathered together about 4,000 followers at the moment which no doubt will grow rapidly as his fame spreads far and wide!

Natalia and Fedya. Photo: Instagram/Natalia.

The best guess is that the startled look is simply the way his face is built. You get this sometimes. It's about facial anatomy and is just in the lap of the gods as to whether cats end up with these fixed expressions which are quite rare. All the former cat celebrities have some sort of facial deformity. It is a inherited skeletal condition. It does not affect his health as far as I know.

Neighbour's cat called Handsome helped nurse Fedya back to health when he was a rescued stray kitten. Photo: Instagram/Natalia.

Apparently, when he was found he also had "wonky legs". And his eyes were misaligned. That is why they say that he looks permanently startled but that isn't the reason in my opinion because his does not look cross-eyed like a Siamese cat. His eyes look quite well aligned to me. They just look wide open, very round and stuck in the middle of his very large round, chubby-cheeked head!

What wild cats are black?

No wild cat species (as a species) is black. Sometimes individual wild cats of some species are black or dark charcoal because of a genetic mutation resulting in melanism. The classic melanistic wild cat is the black jaguar called the black panther. The puma can be black too and so can the bobcat, the serval, the leopard and Geoffroy's cat. These names come out of my head. I have probably forgotten some.

Black leopard (melanistic). Pic: Pixabay.

But the point is that the answer is NONE. It is just that some individuals do end up black against the usual colour of the species concerned because of this genetic mutation.

SEE SOME BLACK PANTHER PICTURES.

Melanism affects many animals of many species, not just some wild cats. For instance melanistic leopards are quite common. They are sometimes bred in zoos. Black leopards are caused by a recessive gene. They are less fertile than normal leopards according to Sarah Hartwell, a cat genetics expert.

Black leopards in captivity may be more highly strung than normal leopards because they are bred to entertain the public and in doing that they become inbred. This affects their mental health. 

As leopards are nocturnal being black does not impede hunting but probably has the opposite effect. Melanistic leopards are also called black panthers.

Should we genetically engineer cats to curb their urge to kill?

Not long ago I proposed genetically engineering feral cats to make them infertile as an alternative to TNR programs which includes spaying and neutering. But it might be a better idea to genetically engineer feral cats. That would seem to be a more elegant way to control the feral cat population. I don't know whether it's been discussed but what is also being discussed is genetically engineering cats to modify their behaviour, to stop their urge to kill.

Photo: Pixabay

That would mean altering the most fundamental aspect of a cat's behaviour which is to hunt, stalk, attack, kill and eat prey animals. In the case of domestic cats that usually means small mammals such as voles, mice and even rats occasionally (plus reptiles, birds and insects). I'm not sure if it is viable. I'm not a good enough scientist to decide how you'd go about doing that.

The obvious initial downside is animal testing. I can see animal testing taking place which would be cruel. I could not justify it. I don't believe that any animl testing is ethically and justifiable today. It is time to stop it.

You can achieve character changes to a certain extent by selective breeding. This is breeding through artificial selection so you only select those cats which are very passive and mild mannered with a known trait of a disinterest in hunting. That might be hard to believe but some domestic cat hardly hunt at all whereas others are obsessed with it such as my cat!

The average domestic cat will certainly enjoy hunting to a certain extent but it would seem fair to suggest that we could select the least motivated hunters and selectively breed from them to the point where you only had domestic cats that were disinterested in what should be their primary activity: hunting.

Brief research tells me that that scientists genetically engineer animals by introducing a beneficial gene into their DNA. I suppose, therefore, it would mean scientist deciding which genes and on which chromosomes behavioural traits such as hunting are located. 

Then they could remove those genes and replace them with the genes of a cat with known traits including a disinterest in hunting. I'm guessing wildly at this point. But the concept of genetically engineering cats to modify their behaviour to eliminate hunting is fascinating but it seems to be a bridge too far at this stage. What do you think?

The Lack of a Sweet Tooth in Cats

Domestic cats are neither attracted to nor avoid the taste of sweet carbohydrates. In an extreme adaptation to a carnivorous diet, the domestic cat has taste buds which are very responsive to amino acids but unresponsive to many mono and disaccharides (carbohydrates).

By contrast, many dogs have a sweet tooth and prefer natural sugars, for example: sucrose, fructose, glucose and lactose but not maltose.

Cats and dogs respond very differently to stimuli which is sweet tasting although both as we know our carnivores.  The dog is, it seems, a borderline omnivore. Domestic cats find bitter tastes objectionable. Dogs should not eat cat food and vice versa.

The sweet receptor or taste buds that can taste sweetness are made up of two “coupled proteins" which are generated by two separate genes.

The domestic cat, and in fact all cats, lack the amino acid that make up the DNA of one of these genes.

Cats are the only mammals lacking what is called the “sweet gene".  Despite this well-known fact major pet food manufacturers use corn (24% carbohydrates) and other grains in their food. It has been postulated that this is a reason why an ever-increasing number of domestic cats are becoming diabetic.

Modern dry cat food today has around 30% carbohydrates and cats can't handle it which when we think about it is a bit shocking.  I wonder whether millions of cat owners realise that.

Cats cannot taste the sugars in dry cat food but they are doing the cat harm.

Genetically Engineered Bengal Cat

Some people think that the Bengal cat is "genetically engineered" because they search for information about this subject. This cat breed is not genetically engineered on the standard definition of that phrase. "Genetic engineering" could be defined as "the direct human manipulation of an organism's genome using modern DNA technology".

Photo: Helmi Flick.

The Bengal cat is a simple hybrid. There are many breeds of cat that are hybrids. Most are domestic cat to domestic cat matings such as the Burmilla. These are breeds created by mating a cat of one breed with a cat of another breed. Cat breeds though are all one species of cat (the domestic cat - felis catus).

There are some wild cat to domestic cat matings that occur naturally. The wildcat hybrids such as the Bengal and Savannah (and Safari) are deliberate matings of wildcat with domestic cat, however. This though is not genetic engineering.

Genetics of the Burmilla Cat

The coat is short. There is a white undercoat, profusely shaded with tipping. The colours allowed for the Burmese are allowed for the Burmilla. The basic genotype is A-c^bc^bI- to which should be added the genes that create the colored varieties. The dominant gene: I, produces the white undercoat.

The shaded Burmilla is agouti. The agouti varieties are called Asians. The jet black Burmese (a non-traditional colour) is called a Bombay.






From Genetics of the Burmilla Cat to Home page.

Cat Coats White

Cat coats white is the last in a series on the cat coats. See all the articles by clicking on this link. In previous articles I have mentioned the Piebald gene (White Spotting gene). The gene usually (denoted by the letter "S") produces coats with white "spots" although "spots" is a misleading term. It produces areas of white leaving other areas in a wide range of colors and patterns such as Tuxedo, Tabby, solid colors and others (it is perhaps best to see all the posting to get the complete picture). 

All-white Maine Coon

 As can be expected if the white spotting works to maximum effect, then the whole of the cat will be white instead of areas of white, either small or large. Accordingly, one of the three genes that produces all white cats is the white spotting gene. Its actions are wide ranging as can be seen. That's why it is said to have "variable expression". It is called "recessive white" sometimes and I suppose because of its variable actions, it is "semi-dominant". 

 The genes that produce white fur cover up the other colors. Note: Albino cats are due to a different effect, the lack of production of color (see below). 

The other gene that produces cat coats that are white is the dominant white gene ("W"). This gene masks all other colors. 

As a result, it is impossible by looking at the cat to see what other genes are present. To use technical language, the gene W is "epistatic" meaning it masks all other color genes. There may be an exception in relation to eye color. The dominant white gene is a simple non sex related dominant gene. The white cat is not due to the presence of a number of piebald (white spotting) genes. 

Russian-bred all-white British Shorthair kitten. Photo: Альбина Шконда питомник британских кошек Golden Leris nursery Golden Leris. WCF.

The W gene is at a different position on the chromosome to the white spotting gene and is therefore independent of the white spotting gene. Epistatic crudely means that where there is a competition between genes as to what color or type of coat will be seen (for genes involved with coat color), the gene whose phenotype (the appearance) is expressed (the appearance seen) is said to be epistatic. 

The W gene is also associated with deafness as it can affect the cochlea in the inner ear (the fluid filled chamber that converts sound waves to nerve transmissions to the brain). The gene produces blue, orange or odd eyes. If the cat has blue eyes there is a good chance that he/she will be deaf as well. If she has one blue eye, there is a good chance that she will be deaf in the ear on the side of the blue eye. 

As the name of the gene implies this is a dominant gene so if fully present its effects are produced (from genotype - the genetics to phenotype - the physical result). In a survey of 185 cats, one quarter had normal hearing and yellow eyes, 31% had normal hearing and blue eyes, 7% were deaf and had yellow eyes and 37% were deaf and had blue eyes. 

 The third and highly unusual genetic make-up that results in all-white cat coats is the albino. This is complicated genetically so a brief mention is probably best. There are alleles that are known to produce albinism. 

An allele is one member of a pair of genes at a certain point on the chromosome. The alleles concerned are blue-eyes albino, pink eyes albino, Burmese Pattern, Siamese Pattern and full color (ref: Sarah Hartwell). These cats have pink eyes. The all-white cat is more prone to contract skin cancer as the skin more readily absorbs ultraviolet light. This should be born in mind by keepers of white cats in hot climates. Source:

• Messybeast
• Robinson's Genetics
• Me