Cat owners will recognise the purr of pleasure from their pets when they are tickled behind the ears, but a new analysis comparing the domestic cat’s genome with that of its wild relatives suggests this may also have been key to taming the animals in the first place. 
 
 The analysis has identified some of the crucial changes in feline DNA that have occurred as the animals were domesticated over the past 9,000 years. Among the main differences are changes in genes associated with the growth of brain cells involved in feelings of reward and pleasure. 
 
 This suggests that humans first began domesticating these notoriously solitary creatures by appealing to their desire for treats and stroking. Those that responded were then more likely to be bred, leading to increasingly docile animals as time went on. 
 
 “You can imagine wild cats picking up scraps of food from near to human settlements initially and gradually becoming more accustomed to human presence,” said Dr Bronwen Aken, one of those involved in the research at the Wellcome Trust Sanger Institute in Cambridge. “They would have moved in closer to the point where they were being fed. The food would probably have been the primary reward and petting would have come later.” 
 
 Cats are thought to have been first domesticated around 10,000 years ago from the Near Eastern wildcat, which can still be found roaming the Middle East. Archaeological evidence for domesticated cats has been found in Cyprus dating back 9,000 years, while Chinese farmers are known to have been living with domestic cats 5,000 years ago. 
 
 Domesticating wild cats would not have been an easy process, however. The Near Eastern wildcat, from which almost every breed of household cat alive today is thought to originate, is notoriously shy and spends most of its life as a solitary animal. 
 
 But the new research provides some hints about how our human ancestors may have done this. By comparing the genomes of 22 domestic cats from around the world with those of European wildcats and Near Eastern wildcats, researchers identified 13 key genes that differed, including genes involved in the reward centres of the brain and the development of neurons that are key to producing dopamine – the so-called pleasure hormone. This suggests that the first wild cats to be bred for domestication were those that had responded to offers of rewards such as food and stroking. 
 
 The research, which is published in the journal Proceedings of the National Academy of Sciences, also shows that domestic cats have genetic differences in areas related to fear conditioning and memory. The scientists believe changes in memory were another response to being fed and rewarded by humans. 
 
 “When compared to wild cats many of the differences in domestic animals appear to be in genes that result in behavioural changes,” said Dr Aken, who now works at the European Bioinformatics Institute. “But when you look at cheetahs and lions in Africa, you can still see a lot of similarlities in their body language like the way they flick their tails when annoyed. 
 
 Dr John Bradshaw, an expert on domestic cats from the the University of Bristol who helped conduct the research, said: “Many of the domestication genes seem to impact development of the nervous system. 
 
 “There is an idea, known as the neural crest hypothesis, that the way the nervous systems of domestic animals is laid down is different from wild animals, bringing things like a lack of fear, and this is the first genetic evidence that this might be happening.” 
 
 The new study shows, however, that domestication did not eliminate the predatory nature of wild cats and helps to explain why as pets they still kill birds and rodents despite having an abundance of food. 
 
 By comparing wild cat genomes with those of domesticated cats, dogs, cows and humans, the researchers found that all cats share six genes that appear to give them hearing over a far wider range of frequencies than other species. They also found mutations in genes associated with vision that the researchers believe give the animals better eyesight in low light conditions. These characteristics were probably desirable as domestic cats were used to help control rodent populations on farms and around homes. 
 
 However, cats have far fewer genes associated with smell – around 700 – when compared with dogs, which have more than 800. ||||| It may not surprise the average cat owner, but a team of researchers has discovered that the genome of domestic mousers differs only slightly from that of wildcats. 
 
 In other words, after 9,000-odd years of living alongside humans, the house cat remains only semi-domesticated, according to a report published this week in the Proceedings of the National Academy of Sciences. 
 
 After comparing the genome of an Abyssinian cat named Cinnamon with those of humans, tigers, cows, dogs and another cat breed known as the Birman, the scientists found that cats retain many of the hunting, sensory and digestive traits of their wild kin. 
 
 Researchers did find a signal for human influence on cat evolution, however, in fur color and pattern, as well as a set of genes that are thought to be associated with tameness. 
 
 “We believe we have created the first preliminary evidence that depicts domestic cats as not that far removed from wildcat populations,” said senior author Wes Warren, an associate professor of genomics at the Genome Institute at Washington University in St. Louis. 
 
 The discovery that as few as 13 genes may separate domestic cats from their wild ancestors was a “genuinely important” advance, according to John Bradshaw, an anthrozoologist at the University of Bristol School of Veterinary Sciences in Britain, who was not involved in the research. 
 
 “This can only be the beginning of what will surely lead to a revolution in cat breeding,” Bradshaw wrote. 
 
 By pinpointing genes responsible for cat behavior and temperament, humans could more easily guide more changes in the animal. 
 
 “The potential is there to finally guide the cat through the remaining stage of domestication, not only producing cats that are better adapted to the demands of 21st century living, but at the same time enhancing their well being,” Bradshaw wrote. 
 
 Unlike dogs, which some researchers say began their association with humans roughly 30,000 years ago, archaeological evidence suggests that cats first entered our living space when we began to grow crops, about 10,000 years ago. 
 
 Researchers hypothesize that early farmers welcomed the felines because they hunted grain-eating rodents. Farmers rewarded the efficient rodent-slayers with extra food, researchers say. 
 
 Yet it's only in the last 200 years that humans have placed intense selection pressure on cats, producing up to 40 different breeds, Warren said. 
 
 Warren and his colleagues said that this relatively short period of breeding was partly responsible for the modest influence domestication has had so far on the evolution of Felis silvestris catus. However, it wasn't the only reason. 
 
 “Most importantly, some continue to interbreed with wildcat populations,” Warren said. 
 
 When examining the cat's genetic makeup, the researchers found that the animals retained qualities of wild hypercarnivores — hunters that eat meat almost exclusively. 
 
 “Carnivores are endowed with extremely acute sensory adaptations, allowing them to effectively locate potential prey before being discovered,” the authors wrote. “Within carnivores, cats have the broadest hearing range, allowing them to detect both ultrasonic communication by prey as well as their movement.” 
 
 In addition to retaining visual acuity that enables them to hunt in low-light conditions, cats are also able to metabolize high-protein, high-fat diets. 
 
 “Cats fed a diet rich in saturated and polyunsaturated fatty acids showed no effects on plasma lipid concentrations that in humans are risk factors for coronary heart disease and atherosclerosis,” the authors wrote. 
 
 Researchers have hypothesized that the cat's peculiar, meat-intensive diet is one of the reasons it has existed on the edge of domestication. Dogs can be kept and bred on a vegetarian diet, which is much more difficult with cats. 
 
 Prior to the development of nutritionally sustaining pet foods, cats most likely had to rely on their hunting skills to obtain sufficient meat. 
 
 Though breeding of cats has focused mostly on controlling hair color and pattern, the authors identified gene changes that some researchers say are associated with the “domestication syndrome hypothesis.” 
 
 That hypothesis argues that when animals are bred for domestication, changes occur in a group of embryonic stem cells called the neural crest. These changes can result in diminished fearfulness and other qualities that appeal to humans. The hypothesis has yet to be proved experimentally, however. 
 
 “Our results suggest that selection for docility, as a result of becoming accustomed to humans for food rewards, was most likely the major force that altered the first domesticated cat genomes,” authors wrote. 
 
 Today, it's believed that there are as many as 600 million cats worldwide. 
 
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– Cats aren't dogs, and they'd like us to remember that, an animal behavior expert tells the Telegraph. We stress them out by expecting them to be as sociable as our canine friends, happy to be petted and hang out in the same space as other cats. But that just doesn't fit with how cats think, says Dr. John Bradshaw. "Dogs were sociable before they were domesticated," he says. "Unlike dogs, the cat is still halfway between a domestic and a wild animal, and it’s not enjoying 21st-century living." And when a cat is stressed, it can develop dermatitis and cystitis, he notes. In the past, "with cats, all we wanted was for them to keep our houses and farms and food stores free of rats and mice, and they got on with that," Bradshaw says. “It’s only in the last few decades that we have wanted them to be something else." That's not to say your cat doesn't love you, he adds. It's just that they "have their own lives" and interests. (And, as he told the Huffington Post earlier this year, your cat probably also thinks you are a very large cat; that's why, he theorizes, they communicate affection with humans the same way they do with other cats.) Some tips: Cats are likely to spend more time with you if they approach you, rather than if you approach them first, according to research, he notes. And if you're planning to get a second cat, you might want to bring its smell home first on a handkerchief: "It’s the cat equivalent of exchanging photos before a blind date." (Read about a cat who lived secret lives with two families.)