Washington - A mild manner and a fondness for fatty treats like fish or meat scraps may have helped cats evolve into the tame yet independent-minded pets they are today, researchers said on Monday.After that, it was people's preference for cats with certain appearances, like white paws, that played a key role in winnowing down the 38 species known today, said a study."Using advanced genome sequencing technology, we were able to shed light on the genetic signatures of cats' unique biology and survival skills", said Wes Warren, associate professor of genetics at the Washington University School of Medicine.Domestic cats "only recently split off from wild cats, and some even still breed with their wild relatives. So we were surprised to find DNA evidence of their domestication", he added.By comparing domestic cat genes to other cat breeds, as well as wildcats and other mammals, certain differences stood out.For instance, tigers and domestic cats each have the uncanny physical ability to eat lots of fatty acids without the resulting heart disease and cholesterol that such a diet would have on humans.In fact, cats need meat in order to thrive, whereas most other carnivores can and do survive on a diet of plants, grains and legumes."The team found particular fat-metabolising genes in carnivores such as cats and tigers that changed faster than can be explained by chance", the university said in a statement."The researchers did not find such changes in the same genes of the cow and human, who eat more varied diets and would not need such enhancements."Evolved sensesCats rely less on smell than dogs do when it comes to hunting, but they have better night-time vision and hearing, the study found.Cats also have more genes related to the ability to sense pheromones than dogs, a trait that helps them to find mates even at a considerable distance.Pet cats showed clear signs of genetic selection in traits related to memory, fear conditioning and stimulus-reward learning, suggesting that more docile cats were likely preferred as pets.Genetic selection for appearance was also evident, particularly in recent generations."Unlike many other domesticated mammals bred for food, herding, hunting or security, most of the 30-40 cat breeds originated recently, within the past 150 years, largely due to selection for aesthetic rather than functional traits", said the study.For instance, the Birman cat breed likely developed its characteristic white paws because humans chose to breed cats that looked the same.In the random population of cats, the genes that lead to the gloving pattern are only seen in about 10 percent of felines.Rodent killersAbout 600 million cats exist on Earth. The earliest archaeological evidence of cats living with people dates back 9 500 years to the Mediterranean island of Cyprus.Archeological evidence of cats as pets has also been found 5 000 years ago in central China.Cats are believed to have worked their way into humans' everyday lives during agricultural periods in history, when their work as killers of rodents and vermin would have been prized."Most cats were likely bred for rodent control, and only later for pigmentation", said study co-author Michael Montague, in an email to AFP."In a sense, tameness would need to be one of the initial behavioural differences between wildcats and domestic cats and perhaps the ultimate driver of domestication."