One of the oldest pieces of archaeological evidence of humans and cats living closely together is a human grave discovered in Cyprus, where a person was buried alongside a cat. Because cats are not native to Cyprus, people must have brought them over by boat, suggesting a close bond.
The grave was dated to at least 7,500 years ago and may be as old as 9,000 years.
The Cyprus cat may not have been completely domesticated. Like humans who keep raccoons or possums as pets, it's probable that this particular cat was raised as a kitten and attached itself to the family, realizing that it could get easy meals and a comfy place to sleep if it caught a few mice. Even then, cats weren't dumb.
The human-cat connection is one of the newest examples of domestication in the animal world. Now, we're finding that at least part of that connection is hormonal in nature for both humans and the cats who are kept by them.
"Scientists in Japan looked for signs of that connection in two hormones," writes ScienceAlert's Esra Oz. "Oxytocin plays a role in social bonding and can rise during affectionate contact. Cortisol helps regulate the body's response to stress and its use of energy."
The study, published in iScience, found that owners with higher oxytocin tended to have cats with higher oxytocin, too. Higher cat oxytocin was associated with fewer negative emotions and less cortisol in the system of their human companion.
The researchers speculate that the act of petting leads to the creation of these hormonal connections, author Saho Takagi of Kyoto University told ScienceAlert.
"I think this may be because oxytocin rises in both the owner and the cat through the petting-and-being-petted interaction, and that this interaction helps to form their bond," Takagi said.
Cats can form close bonds with their humans. But the physiology of that relationship remains less explored. According to the researchers, no earlier study had measured oxytocin in both cats and their owners.
Takagi and her colleagues recruited 19 owners and their 29 pet cats. The hormone comparison used data from the 24 cats whose urine could be collected and their 17 owners.
The team averaged measurements from three urine samples for each individual. Owners also completed a questionnaire about their feelings over the previous few weeks. Small Bluetooth beacons on the cats' collars sent signals to their owners' phones. These signals helped estimate how close they were at home.
The two hormones have other functions besides bonding and mood. Oxytocin, produced in the brain, also plays roles in childbirth and milk release, while cortisol levels vary throughout the day. Also, cats were not always cooperative about when they urinated.
Big surprise.
The cat wore a Bluetooth beacon to track its movements throughout the day and estimate its proximity to its owner. "The devices could not reveal what happened during those encounters," says Oz. "A cat sleeping beside its owner and a cat being stroked could produce similar signals. The role of particular behaviors therefore remains unclear."
In a separate exploratory behavioral test, cats with higher oxytocin were more likely to approach a person sitting inside a marked circle. That person could be their owner or a stranger.
There was no clear association between cats' and owners' cortisol. A 2019 dog study had found a connection between cortisol in canine fur and human hair.
The studies used different methods. In the new research, human urine was collected in the morning, while cat samples were collected whenever possible. Timing differences may have made a cortisol association harder to detect.
The oxytocin connection also does not show hormones rising and falling together. The researchers compared average concentrations. They did not test whether changes over time in a cat accompanied similar changes in its owner.
"To call a finding 'synchrony,' I think hormones would need to be measured at multiple time points and shown to change in a similar way over time," Takagi explained.
Everyone I know who has a cat companion feels that connection strongly, especially when the cat is in close proximity to their human friend. Cats crave human contact (when they want it, of course) and are never more relaxed than when snuggled up with their human companion.
Call it "hormonal," or call it something else; the connection to a cat is mystical. With dogs, you expect the connection. It's no less powerful, though a cat is more discerning about who it attaches itself to.
One day, AI will make it possible for us to communicate with our cats. That will be a sad day. It will take some of the mystery of cats away and make them a little less inscrutable.
