Cuteness, it would seem, is one of life’s most endearing evolutionary strategies – and one that felines have hijacked to remarkable levels. For cat lovers, our furry feline friends are akin to our closest companions, and this is reflected in our neurobiology: being close to them triggers activity in the same emotion-processing region of the brain. Even when we’re not sharing precious moments in real life, we merely have to turn to our phones to get our fix. Cats, after all, do the funniest things. But what is it about them that we find so adorable?

Cats are distinctive animals: domesticated for centuries, revered and reviled in equal measure throughout history and bred to match our own aesthetic tastes and whims.  From a sensational internet fluffball to his own domestic longhair Loki, renowned animal photographer Tim Flach explores the world of cats in his new book , showing how intertwined our lives have become.

“At the heart of this project was to unmask the essence of feline,” says Flach. Including more than 170 of Flach’s cat images, Feline also sees neuroscientist Morten Kringelbach explore why we find felines so compelling, and evolutionary biologist Jonathan Losos delve into the species and its evolution.

Pictured above is Stella, a Cornish Rex from Montreal, Canada, whose striking appearance is a result of genetic quirks during her embryonic development. Cats with different-coloured eyes almost always have one blue eye, writes Losos. The phenomenon is particularly common in entirely white cats.

Flach also includes shots of feline internet sensations such as Atchoum, below, a long-haired Persian with a rare condition called hypertrichosis, which causes his hair to grow profusely. Currently, Atchoum has more than 900,000 followers on Instagram.

Elsewhere, Zuu, an exotic shorthair, takes cuteness to the extreme – a perfectly round fluffball that’s impossible to resist (below).

Cuteness, writes Kringelbach in Feline, is how mammalian and avian babies elicit care from elders, compensating for their helplessness. Big eyes, rounded features and large heads are typical baby features that humans (and many other species) find irresistible, and have been shown to trigger activity in the orbitofrontal cortex, an emotion-processing region of the brain. The idea is that if our brains reward us for looking at and providing for babies, it makes it easier for our species to survive. But this response is not restricted to our own species. Cats, too, trigger this same reward zone in humans.

By scanning his own brain as it responds to Loki, his domestic longhair, Flach highlights the cuteness effect and how his orbitofrontal cortex lights up within 130 milliseconds, much faster than conscious thought. “In a way, at some fundamental level, you can see how cuteness is unfolding,” he says.

But cuteness is just one of cats’ evolutionary advantages.  They are perfectly adapted for a life of hunting – as demonstrated by this 8-week Sphynx cat Valentine, below, which is leaping for a cat toy just out of sight.

A cat’s nose has as many as 40 times more scent-detecting cells than a human’s. Cats’ whiskers are finely tuned to detect subtle vibrations, helpful for moving in the dark and hunting at close range. Their tongues, too, are uniquely fashioned. Covering the organ are small papillae, or spikes, made of keratin – the same material as in our nails and hair.  This roughness is useful in grooming, eating and drinking. But the tongue also plays a role in cats’ sense of smell, transferring pheromone scents to the vomeronasal, or Jacobson’s, organ at the roof of the mouth.

But it is cats’ eyes that are perhaps their most alluring feature. In the past, superstition suggested that a cat’s bright eyes were indicative of a devil glowing back. In reality, the glowing orbs that shine back at you if you point a light at a cat in the dark are the result of special reflective cells known as tapetum lucidum, which reflect unabsorbed light back to the photoreceptors (rods and cones) in the retina. Cats have a much greater density of rods than humans, and are also able to widely dilate their pupils, enabling them to see at light levels six times lower than humans, writes Losos in his book.

To capture cats’ eyes for Feline, Flach and his team used special lenses and high-speed flash to show them in ways never before seen, to “show it almost like a lighthouse light, like a mirror”, says Flach.

A new coat colour pattern has emerged in cats across Finland, and scientists have just identified the genetic mutation responsible for it.

The fur on the backs of these cats is coloured only at the base near the skin. Each hair progressively gets whiter towards the tip, and the tips of their tails are usually white as well. Otherwise, the cats share the classic “tuxedo” pattern that features an all-white neck, chest, belly and paws – although spots of colour sometimes cover parts of the white markings, says at Mars Petcare Science & Diagnostics in Helsinki.

Anderson and her colleagues have dubbed the new coat “salmiak” because the colouring resembles that of the popular Finnish salty liquorice of that name, she says.

People first noticed the unusual fur patterns – which became known originally as “the Finnish mutation” – in three cats in central Finland in 2007. In 2019, researchers at the University of Helsinki reached out to Anderson, a specialist in feline genetics, after learning about another “Finnish mutation” cat.

Together, the researchers sought out more such cats throughout Finland via media announcements, says Anderson. When DNA testing on the cats turned out to be negative for all the gene variants already known to affect white colouring in cat coats, the researchers decided to dig deeper.

They sequenced the entire genome of two of the cats and found a mutation at a chromosome site very close to the KIT gene, which is associated with various white hair patterns in many domestic animal species. “There was a huge chunk of sequence missing downstream from the KIT gene,” says Anderson.

The researchers then created a specific test for the newly discovered variant to confirm that it was responsible for the fur pattern. Out of the 181 additional Finnish house cats they tested, only three had salmiak coats – and each of these had inherited the variant from both of its parents. Another three cats had inherited the variant from a single parent, and the remaining 175 didn’t have the variant at all.

The findings confirm that the team has identified the recessive mutation that leads to salmiak fur, says Anderson. “These coats have aroused a lot of admiration for years,” she says. “It’s really exciting that we now have some genetic explanation for it.”