Cat breeds are created by selectively mating cats that share specific physical traits, then repeating that process across enough generations that the traits breed “true,” meaning kittens reliably look like their parents. The entire concept is surprisingly recent. The cat fancy is less than 150 years old, and most of the breeds you see today were developed in just the past 50 to 75 years. The International Cat Association (TICA) currently recognizes 73 breeds.
What Makes a Breed a Breed
Unlike dogs, which were historically bred for jobs like herding, guarding, or hunting, cat breeds have been shaped almost entirely around appearance. Human selection in cats has focused on aesthetic qualities like coat color, fur texture, ear shape, and body proportions rather than complex behaviors or working abilities. This is one reason cats across breeds tend to behave more similarly to each other than, say, a border collie behaves compared to a bulldog.
A breed becomes official when a registry accepts it. Each registry (TICA, the Cat Fanciers’ Association, the Governing Council of the Cat Fancy in the UK, and others) maintains its own list and its own standards. A “standard” is a written description of the ideal version of that breed: how the head should be shaped, how long the tail is, what coat colors are allowed, and so on. Breeders select cats that best match these standards and mate them together, generation after generation, to keep the look consistent.
How New Breeds Get Started
Most breeds begin when someone notices a naturally occurring mutation in a litter of ordinary cats. A kitten born with folded ears, unusually short legs, or curly fur catches a breeder’s attention, and they begin mating that cat with others to see if the trait passes to offspring. If it does, they work to establish a stable population that consistently produces the trait.
Getting a new breed recognized is a multi-stage process. Registries typically require breeders to first gain “name recognition,” which allows the cats to be registered and shown in exhibition classes but not compete for championships. From there, the breed must demonstrate that it is genetically distinct from existing breeds, has a large enough breeding population, and follows a written standard. The UK’s Governing Council of the Cat Fancy uses a traffic-light system: green means a breed will likely gain acceptance if good evidence is provided, amber means the breed is based on a trait that could cause welfare problems and the burden of proof falls on the applicant, and red means scientific evidence already links the breed to serious health issues, making recognition unlikely.
The Genetics Behind Breed Traits
Every distinctive breed trait traces back to a specific gene or set of genes. The Scottish Fold’s signature folded ears, for example, come from a variant in a gene called TRPV4, which also affects cartilage throughout the body. The Sphynx cat’s hairlessness results from a mutation in a gene involved in building the protein structure of hair (KRT71). The Devon Rex shares a mutation in the same gene but at a different location, which is why both breeds have unusual coats but look quite different from each other.
Coat color works through a surprisingly elegant system. Cats produce two types of pigment: one that creates black-to-brown shades and another that creates red-to-cream shades. A molecular switch on each pigment-producing cell determines which type gets made at any given moment. When the switch is “on,” cells produce dark pigment. A small signaling molecule can flip the switch “off,” causing cells to produce lighter, yellowish pigment instead.
This switching mechanism explains the tabby pattern. In tabby cats, the signal pulses on and off during hair growth, creating individual hairs with alternating dark and light bands. That banding is what gives tabbies their characteristic ticked, warm-toned look. Solid black cats, by contrast, carry a mutation that permanently disables the “off” signal, so their pigment cells stay locked into dark-pigment mode throughout the entire hair growth cycle. A cat needs two copies of this broken version to appear solid black, which is why two tabby cats can occasionally produce a solid-colored kitten if both carry one copy.
Why Purebred Cats Are Genetically Narrow
Breeding for specific looks comes with an unavoidable genetic trade-off. When you repeatedly mate cats that look similar to each other, you reduce the genetic variety in the population. Research comparing pedigreed cats to random-bred cats worldwide found that about 24 to 27 percent of the total genetic variation in cats sits between breeds rather than within them. That’s a large chunk of diversity being parceled into separate, isolated pools.
One way to measure this is by looking at how many unique gene variants a breed has compared to the broader cat population. When researchers counted breed-specific genetic markers, most breeds had between zero and two that weren’t also found in random-bred cats around the world. In other words, breeds aren’t built from exotic new genetic material. They’re built by concentrating a narrow selection of variants that already exist in the general cat population and filtering out the rest.
The genetic diversity within individual breeds varies widely. Some breeds have relatively healthy diversity levels, while others are quite restricted. Observed genetic diversity across breeds ranged from 0.34 to 0.71, a spread that reflects how differently each breed’s population has been managed.
Health Consequences of Selective Breeding
Narrowing a gene pool doesn’t just affect appearance. It increases the chance that a kitten inherits two copies of a harmful recessive gene, one from each parent, which can cause disease. In a genetically diverse population, harmful recessives stay hidden because cats rarely inherit the same rare variant from both sides. In a small, closed breeding population, the odds go up significantly.
The practical effects show up in reproduction. A Swedish study found that British Shorthairs, Birmans, Persians, and Exotic Shorthairs were overrepresented in cases of difficult births and stillborn kittens. Breeding for traits like flat faces (brachycephalism) didn’t directly reduce fertility, but it increased the rate of complicated deliveries and kitten loss. Research also found a trend toward more neonatal deaths and birth defects as inbreeding levels rose, including malformations like cleft palates and limb abnormalities.
The cheetah offers a dramatic example of where extreme genetic narrowing leads. Wild cheetah populations went through a severe population bottleneck thousands of years ago, and the consequences persist today: reduced fertility, high death rates among newborns, and over 75 percent of sperm cells being abnormally formed, compared to about 29 percent in domestic cats. Cat breeders work to avoid this kind of collapse by outcrossing to unrelated lines, but the fundamental tension between maintaining a “pure” look and maintaining genetic health is baked into the system.
Breeds vs. Mixed Cats
Only a small fraction of the world’s cats are pedigreed. The vast majority are random-bred, meaning their ancestry reflects generations of unmanaged mating across genetically diverse local populations. These cats still carry the same genes that define breed traits. A random-bred black cat has the same pigment mutation as a pedigreed Bombay. The difference is that the Bombay’s entire genome has been shaped by intentional selection, while the random-bred cat’s genome is a freer shuffle of whatever was available in the local gene pool.
This is why calling a mixed cat a “breed” based on appearance alone doesn’t really work. A fluffy gray cat with a round face isn’t part Persian just because it looks vaguely similar. Breed identity is defined by documented lineage, not by coat type. Registries require multi-generation pedigrees before a cat qualifies as a member of any breed, precisely because so many traits crop up independently in unrelated populations around the world.