How old is your dog in human years?

It’s a question many pet owners ask themselves: If my dog were a human, how old would he be? For many years, simply multiplying by 7 was enough to calculate the difference. But in a new study, scientists are challenging this paradigm. It was already known that the “rule of 7” wasn’t very accurate. A 9-month-old dog can have puppies, whereas a child who is just over 5 years old clearly cannot. The equivalence isn’t linear. Dogs seem to age more rapidly at first and then slow down as they get older. While at first glance the aging trajectories appear similar (graying, increased susceptibility to disease with age, etc.), aging at the molecular level differs . What is surprising is the distortion of the curve. A one-year-old dog is actually equivalent to 30 human years. According to a new, much more precise calculation formula, dogs are likely much older than previously estimated. In any case, that is what the chemical changes in DNA—caused by the aging of organisms—seem to indicate. DNA, which contains all the information necessary for the development, functioning, and reproduction of every living being, changes very little over the course of a lifetime. This is not the case for chemical markers on the DNA, such as methylation. And for Trey Ideker (@TreyIdeker) of the University of California, the study’s author, these marks are the wrinkles of the genome . “You can guess a person’s age based on markers of aging such as wrinkles or gray hair. Methylation is the equivalent at the molecular level. ” In both species, age-related methylation occurs primarily on developmental genes, which are active in utero and during childhood growth and become inactive in adulthood when the individual stops growing. The researchers studied 104 Labrador Retrievers , ranging from puppies just a few weeks old to 16-year-old dogs, and compared the methylation patterns with those in humans. From this, they derived a more accurate formula for comparing ages: human age = 16 ln(dog age) + 31 . Based on this, an 8-week-old puppy is equivalent to a human baby of about 9 months whose teeth are coming in, and a 12-year-old dog—which is reaching the upper limits of its life expectancy—is equivalent to 70 human years. By focusing on late-stage methylation, the researchers were able to develop, for the first time, a clock capable of measuring age and physiological states across different species. While still a work in progress, this clock could serve as a tool to better understand cross-species aging and could also have clinical implications for the treatment of certain animals. We do not treat an elderly adult the same way we treat a young adult.