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.