Sure, there’s that segment of the population that have never warmed up to cats, but a lot of us out there have a weak spot for all things feline. Be it footage of lions roaming the plains or a YouTube video of a housecat riding a Roomba, face it, we’re more or less all suckers for cute kitties. And this predisposition is more than just a sign of the viral times.
Researchers trying to uncover the full domestication story of the housecat have been finding increasing evidence that the human-feline relationship is rather unique. Unlike dogs, pigs, sheep, cows and horses, our beloved pets’ wild ancestors appear to have chosen to live amongst people, naturally evolving to city life and the accompanying food sources. The cat domestication tale is also much shorter than most other domestics, and it turns out today’s cat don’t actually differ all that much from their wild kin.
‘The domestic cat’s genome is a combed-through version of their wildcat relatives, without new or different genes,’ says researcher Carlos Driscoll. ‘The cats we have in our homes today are the result of the variant allele possibilities for traits we like coming together, aggregating to make a really friendly genotype.’
That’s a huge difference from say dogs, who have been trotting alongside humankind since the time when we still lived in caves and hunted for large mammals. Dogs and wolves are entirely different species, and it shows, but domestic cats are actually a subspecies of Felis silvestris—F.s. catus.
But to fully understand what makes the case of the domestic cat so cool, you need the whole story, which probably doesn’t begin where you’d guess it would.
The first potential proof of cat companionship dates back 9,500 years
Mike Montague with The Genome Institute at Washington University, who helped build the first complete domestic cat reference genome in 2014, says that although the verdict’s still out on the precise origin of cat domestication, one thing is clear—it didn’t happen all that long ago.
‘Our best estimates put the event sometime around 10,000 years ago, somewhere in the Middle East or Southeast Asia’ says Montague. ‘It’s a much more recent domestication onset than most species, and for many, the behavioural differences between cats and older domestic species like dogs is fairly obvious.’
The first direct evidence of cat domestication is cited to a burial site in Cyprus, thought to be from 9,500 B.C., according to Driscoll, a co-author of the 2014 study with Montague. He says it’s hard to decipher precisely why a cat was buried alongside the man in the Cyprus gravesite, but the circumstances of the case point to it being the first documented tame cat with a human.
‘Cats aren’t native to Cyprus, so it had to have been brought in, plus it was fully articulated, suggesting it was killed for the funeral,’ says Driscoll. ‘The inference is this cat was the man’s pet, his favourite or most beloved thing.’
This is a compelling piece of evidence that cats may have been already living with humans, but the next time cats appear to have been heavily highlighted in human society came a great while later.
‘The next evidence we have of cats tied to humans is some 5-6,000 years later,’ says Driscoll, ‘but this time they were noticeably different, over this period transitioning from the wild to living with people.’
The height of feline obsession came in the waning years of the ancient Egyptian empire
This is the part of the story a lot more people are familiar with. While there are many cultures worldwide that revere cats, none have done such with such gusto as the ancient Egyptians. Cats were not only a source of companionship in ancient Egyptian times; they were also a status symbol, religious offering, and source of worship especially in the Late Period, 664-332 B.C.
‘Most people have traditionally cited ancient Egypt as the source of cat domestication, because the culture is popular and sexy,’ says the University of Missouri’s Leslie Lyons. ‘Plus we know these people loved cats, through artwork depicted with the wealthy, not to mention the millions of cats they mummified.’
If you’re into history and kitties, prepare to be jealous. Lyons says she’s played a part in a real life version of Indiana Jones—feline style—searching for cat mummies and still-living wildcat relatives in Egypt back in 2012, thanks to the National Geographic Society and her previous employer, U.C. Davis.
One of the most memorable parts of her trip, explains Lyons, was a tag-along visit arranged by a French archeologist friend to the tomb of Maia, the famed wet-nurse of King Tut. Lyons explains the tomb was built for Maia, but 1,000 years or so later it became a storage facility for sacrificial cats. Priests were probably running out of places to put all those cats, Lyons says, offered up much in the way one lights a votive candle.
‘Standing amongst all those cat mummies, seeing it with my own eyes—it was absolutely one of the highlights of my life,’ says Lyons.
Lyons adds the site is no exception, similar storage sites have been found containing equally massive quantities of mummy cats. She says logic would state this amount of cats couldn’t have come from the wild.
‘Somebody had to get a lot of cats from somewhere,’ says Lyons. ‘This likely means humans were already breeding cats, or had some form of control over them.’
Mummy bones revelations
Lyons says cat researchers had always wanted to look at the ancient genetic secrets of the domestic cat, but it took a long time for the technology to get to the point where this dream could be acted on. And even when the technology caught up, there were plenty of other things to consider.
‘First we had to build up a database from around the world, a cat reference genome, then of course we needed the funding,’ chuckles Lyons. ‘A lot of things had to come together just right.’
Though there’s lots of cat mummies sitting in museums and private collections globally, their owners’ generally don’t want their precious specimens destroyed, or really tampered with in any way. And collecting samples from wild animals is costly, requiring a lot of travel. So when the Brooklyn Museum reached out with samples they were willing to donate to the forensic cause, and the NGS displayed interest in funding the expedition to Egypt to get wildcat samples, Lyons and her team jumped at the chance.
The lab work required to extract and then amplify DNA from the Museum’s mummy bones was pretty intense. The team suited up in full gowns, donning facemasks and gloves, working through the various stages of the process.
‘Many people have touched the samples, so we first have to grind away the outer layers of the bones and clean them, removing common contaminates like fungus and bacteria,’ says Lyons. Then they used tiny drills and chiseling tools to extract a bit of the bone, ground it into a fine pounder and crushed the dust with liquid nitrogen.
The team then isolated mitochondrial DNA from their prepared samples, and using Polymerase Chain Reaction (PCR) technology, amplified regions some 400 base pairs in size. When they compared the cat mummy genetics to their reference database, the results were amazing.
‘The ancient mummy cats turned out to be most like the cats of modern-day Egypt, distinguishable from the cats of Europe, the US, and the rest of the world,’ says Lyons. ‘In essence, you can say the cats of the pharaohs have propagated, and continue to roam the streets of Cairo today.’
Building on the cat reference genome
Lyons says they haven’t had the funding, or sample availability, to further their research, but the next thing they’d like to do is look at the cat mDNA in combination with specific genes. Technology has improved even since their Egyptian study.
Driscoll and Montague are doing precisely that—beefing up the reference genome and helping shed light on the fundamental nature of the human-cat bond along the way.
Though ultimately driven by a medical desire, Montague’s helped sequence the genome of plenty of kitties.
‘We started with a single female cat from Missouri, Cinnamon, whose cell-line was already cultured giving us lots to work with. She also had a visual deficiency of value to veterinary sciences,’ says Montague. ‘After that, we decided to look at all sorts of domestic breeds and wildcats.’
When they combined all this information together the group could directly compare groups of domesticated cats to those in the wild, the findings were rather revealing.
‘Cats weren’t domesticated all that long ago, so we didn’t expect a lot of differences and we didn’t really find many,’ says Montague. ‘But we did see notable differences in genes known to control parts of the brain and its development, genes that when knocked out in mice either increased or decreased their ability to be conditioned with food rewards.’
Comparing the general cat genome to other animals like cows, dogs, and tigers also highlighted cat’s exceptional hearing, capable of hearing sounds at much higher and lower ranges than most other mammals. They also have eye adaptations that make them exception night-hunters and more active pheromone receptors to pick up on the biological perfumes solitary critters like cats use to communicate with one another.
Right now their domestic reference genome, as advanced as it is, is still really in first draft stage, explains Montague. The hope is to go back and iron out the finer details, which ideally would mean sequencing a lot more cats to help decide how genes impact phenotypes, especially those linked with diseases.
‘The last thing on our list is heading out into the wild for samples,’ he says, ‘finding more cats out there doing their own thing.’
Cat domestication was more a product of natural rather than artificial selection
Driscoll says Darwin was the first to point out the unique evolutionally aspect of the domestic cat’s story. Darwin first discussed the idea of artificial selection—the influence of humankind on the breeding of a species—in On the Origin of Species, but went on to further explain his thinking in 1868 in The Variation of Animals and Plants Under Domestication. Darwin notes this process is wholly unnatural, as Driscoll and his co-authors explain in a 2009 PNAS study, beginning somewhere around the time humans first started forming permanent, year-round settlements.
‘For the bulk of human history, the first 150,000 years say, anatomically recognisable human beings existed, we were nomadic,’ says Driscoll. It was only 15,000 years ago or so that places like the Fertile Crescent presented the conditions to live in the same place the entire year, and cities began to form.
‘What makes the domestic cat’s case so interesting is that there was no good reason to bring cats into the human fold,’ says Driscoll. Cats aren’t the great mousers they’re often praised for being—never shown to effectively control rodent populations. And it is unlikely people went out into the wild to capture wildcats.
‘The truth is people coming together and living in communities localised our garbage,’ says Driscoll, which at the time, would have been mostly organic scraps. Drainage pipes and storage silos also created the right conditions for rat and mice hoards—a quick protein-filled meal.
‘Our settlement lured in lots of wild animals,’ says Driscoll, ‘among them, wildcats.’
As cities became more prolific, so did the easy-pickings, and those members of the wildcat population willing to roam into human territory reaped the rewards. This influence was powerful enough to become an evolutionary force, naturally selecting and bringing together the portion of the wild population with city smarts and human-friendly tendencies.
‘Over time, those cats with a natural predilection for cities and humans breed with one another, leading to a fairly well developed domesticated animal,’ says Driscoll. ‘Cats are a rare case of a domestic animal brought about by natural, rather than artificial selection.’
The bigger feline picture
Initially out to help save the critically endangered Scottish wildcat, hoping to determine a way to tell pure wildcats cats from feral domestic-hybrids, Driscoll wound up comparing the genomes of domestic and wild cats from all over the world. His work showed that of all the five sub-species of wildcats, the modern housecat, F. silvestris catus, is most closely related with F. silvestris lybica, living in the Near East.
Yet despite this ancient linkage, people only really began messing around with cat genetics on purpose some 200 years ago, at first heavily in the British Isles. And most breeding efforts had the same aim, producing attractive coat colours and markings. These kind of attributes require alterations in very few genes, sometimes not more than one, meaning domestic cats have retained most of their wild abilities.
Driscoll explains that unlike species humans have selectively breed for thousands of years, like horses or cows, cats have not evolved to expand upon their skill-set, gaining new traits or behaviours to work for us. ‘A feral domestic can do just fine in nearly any condition, and a housecat can do just fine anywhere at all, thanks to us’ says Driscoll. ‘Antarctica is the only place without cats and that is because the Antarctic Treaty says they’re not allowed.’
Feral and house cats alike are often cited with the destruction of a long list of native and endemic species, imposing the pressures inherent of an invasive species. But these four-legged mini-carnivores’ global domination is also causing big problems for the sparse remaining wildcats worldwide.
‘We’ve lost sub-species of felines before, but the Scottish wildcat, continuously diluted by breeding with ferals, may be the first F. silverstris population to go extinct all together,’ says Driscoll.
A geographically isolated sub-population of European wildcats, today F. silverstris grampia has just 250 to 300 members left in the wild. And some of those counted have questionable genetics given that coat-colour is the consideration in classification, Driscoll’s adds.
Sadly, what’s happening to the Scottish wildcat isn’t an isolated case. Worldwide most wildcats face the threat of hybridization, there’s almost no way around it, thanks to the huge amount of feral kitties roaming the planet, still perfectly capable of successfully shacking up with a wild partner. For more than a decade now, researchers have considered there may only be a few, if any, genetically pure wildcats left globally.
In summary, cats came to live with humans because we love them
Some call kitty-loving a vice, and technically, they’re right. No matter how much we adore our four-legged furry friends, the cat-human bond holds no real survival perks for people. It seems the cute and cuddly nature of cats, and their persistence amongst people, has given domestic kitties a big evolutionary edge. They’re effectively insinuated themselves in human populations, as Driscoll stated earlier, without sacrificing much of their wildness.
Of course we’ve left out some smaller parts of the domestic kitty’s tale for the sake of the reader. And there are still a lot of questions left to answer. Just last month French researcher Jean-Denis Vigne and a team of UK and Chinese scientists published a study claiming China’s leopard cat may have formed a bond with humans after the onset of agriculture, just as F.s. lybica did.
Check back with Love Nature to keep up to date as the world’s devoted cat scientists continue to unravel the genetic and historical secrets of our furry friends’ creation story. Knowing cats, there are probably plenty of twists they’re still hiding.