Nearly all dog owners are guilty of performing the math. We look at our beloved pooches and wonder how old they are in human years. For a long time, the 7-year rule provided the answer. Owners simply multiplied their pet’s biological years by seven. In other words, a two-year-old dog is the equivalent of a 14-year-old teenager. In 2019, scientists ousted the popular method as a myth. Instead, they came up with a new formula using genetics.
The researchers published their work on bioRxiv, which is a great scientific analysis for anyone interested in seeing the actual paper. But here’s the gist. Humans and their dogs share something interesting. As we age, DNA activity changes. In particular, methyl groups merge with the DNA and this build-up is roughly what researchers refer to as the “epigenetic clock.” Since this clock already gives a good indication of how people age, the scientists wondered if the same mechanism could determine how old dogs are in human terms.
The team used 104 Labrador Retrievers and picked their DNA apart like good detectives. They focused on a single breed because, as a group, the information about aging in each individual dog was more stable. Afterward, the results were compared with the epigenetic profiles of 320 humans, aged between one and 103. The DNA samples between the two groups were more similar when the scientists compared related age groups. For instance, the pups and kids showed common traits. Elderly members, no matter the species, were also more alike. Once the epigenetic clocks were linked between people and dogs, the scientists could determine the new formula. Interestingly, it showed that 7-week-old puppies were basically 9-month-old humans.
Here is the fascinating new formula: Human age = 16ln (dog age) + 31. Are you interested in testing the method? This calculator will assist in determining your dog’s logarithm, which is marked as “ln,” so that you can insert that number into the formula. Once you’ve entered your dog’s biological years into the calculator, you should get a number. Multiply this digit by 16 and add 31. Now you know what your furry friend’s human age is. Simple, yes? Well, not entirely.
The researchers admitted that their system wasn’t perfect. They only used one breed and dogs age differently, based on their ancestry and size. Dogs also reach puberty faster and can reproduce much earlier than humans. The only phase that was a complete misfit was the bracket that covered adolescence and middle age.
But all things considered, the formula was a step closer to more accurately solve the eternal question of a pet’s human age. Curiously, the 7-year rule has no such foundation. Indeed, nobody knows where or when it became a mainstream belief. Researchers also aren’t sure why pet owners continue to be fascinated by the need to know the answer. But pet lovers know. If anything, the math adds an endearing touch to pets that are already accepted as part of the family.