Researchers comparing the genomes of domestic cats with that of wild felines reveal the genetic underpinnings of domestication. It appears that the conversion from feral to Friskies had to do with genes for memory, fear, and kitty treats. The findings, published in the Proceedings of the National Academy of Sciences this week, could also explain signature cat traits like low light activities and a hypercarnivorous diet.
Cats have been our furry, purr-y companions for at least 9,000 years -- with breeds emerging around 150 years ago -- yet we know very little about their domestication. “Humans most likely welcomed cats because they controlled rodents that consumed their grain harvests,” Wesley Warren of Washington University says. “We hypothesized that humans would offer cats food as a reward to stick around.” Back in August, a team led by St. Petersburg State University researchers reported the whole genome of the domestic cat (Felis silvestris catus) based on a female Abyssinian named Cinnamon who lives in Columbia, Missouri.
Now, to identify genome alterations that led to cat domestication, Warren and colleagues compared Cinnamon’s genome with the genome assemblies of 22 purebreds from six other domestic cat breeds -- the Egyptian Mau, Maine Coon, Norwegian Forest, Birman, Japanese Bobtail, and Turkish Van -- and four wild cats belonging to two species, European wildcat (F. s. silvestris) and Near Eastern wildcat (F. s. lybica). Finally, to get a more complete cat biology picture, they also looked at four other mammals: tigers, dogs, cows, and humans.
“Cats, unlike dogs, are really only semi-domesticated,” Warren says in a news release. “They 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.”
Compared with wildcat genomes, domestic cat genomes showed evidence of recent selection in genes linked to memory, fear-conditioning, and stimulus-reward learning -- which are all related to the evolution of tameness. “They would have needed to become less fearful of new locations and individuals,” Washington University’s Michael Montague tells Science, “and the promise of food would have kept them sticking around.”
Domestic cats also had genetic variations that help explain certain aspects of feline biology, including genes involved in fat metabolism, increased auditory and visual acuity, and a sense of smell that’s different from dogs. To digest their hypercarnivorous diets, cats need genes for breaking down fats; the team found lipid-metabolizing genes in cats and tigers (not humans and cows) that changed faster than can be explained by chance. Cats can hear in the ultrasonic range, and they’re more active at dawn and dusk; accordingly, the team identified genes that evolved to expand their hearing range and low light vision. Finally, cats rely less on smell to hunt than dogs, so it’s not surprising that the researchers found fewer genes for smell in cats. They did, however, find more genes related to an alternate form of smell: the detection of chemicals called pheromones, which allow these solitary hunters to find the opposite sex.