Thanks to Brilliant for supporting this episode of SciShow.

Go to Brilliant.org/SciShow to learn how you can take your math skills to the next level! [♪ INTRO]. It's pretty obvious that dogs age faster than we do.

Like, you might have heard that your dog's age is their human years multiplied by seven. But that is just, like, a made up myth...thing. And we have looked at it scientifically, and what we have discovered is weirder and more interesting than you might think:.

Your dog is aging both more quickly—and more slowly. How old your dog is in human years might seem like a meaningless question. But veterinarians can use that kind of comparison to determine what kind of care their patients' need.

Because, in many ways, dog bodies age much like human ones do. Like, they develop gray hair, and their limbs and joints stop working well. (Not that I would know anything about that!) But the speed at which dogs get old is very different from us: they actually age much faster during the first part of their lives! To get an estimate for how fast, back in 1953, a French researcher lined up major life events in humans and dogs—so, things like puberty and death.

From that, he proposed that puppies age 15 to 20 times faster than people! Like, a one year-old dog is roughly equivalent to a 15 year-old person. Once they fully mature, though, their aging slows down.

And eventually, he thought aging levels out to about a one in five— for every year that passes, dogs age as much as we do in five years. But in a paper published in 2020, researchers from the UCSD School of Medicine showed that dogs age even faster than that — and then, slower. This insight came from looking at measurable marks on DNA that change over time.

These marks are called methylation marks because they're made by the addition of a methyl group: a carbon atom surrounded by hydrogens. Adding a methyl group to DNA can affect whether the genes in that area are active, so patterns of methylation marks across the genome change with things like age and disease. So, the researchers decided to use these patterns to more precisely determine how dog years translate to human ones.

Specifically, they examined the methylation patterns of 104 Labrador retrievers—from few-week-old puppies to 16-year-old dogs. And they compared them to the patterns from humans of varying age, paying especially close attention to developmental milestones in both species. Turns out a one-year-old lab's body has actually aged about as much as a 30 year-old human's!

After about seven years, though, this slows to roughly 1.6 human years of aging per dog year. So, they age much slower than we thought once they become senior puppers. Those exact numbers might not work for every dog, of course.

Previous research suggested that breed and size can impact aging. So, the researchers will need to examine more dogs, and potentially come up with breed-specific age comparisons. Still, these results give us a much better sense of the rate at which dogs are aging.

And that knowledge may help veterinarians better diagnose and treat age-related conditions in them in the future. It may mean they should be testing for some things or providing certain therapies earlier in life, for instance. So even if it seems goofy to think of your four year-old doggo as middle-aged, measuring your pup in human years isn't a silly exercise.

It could help your furry friend live a longer, healthier life. You know, all this talk about aging rates and how they change over time has got me thinking I could use a bit of a math refresher. And luckily, that's something today's sponsor, Brilliant, can help with.

They have more than 60 fun, interactive courses that cover topics in science, computer science, and of course, math. Their new Math History course is really fun. You basically travel back in time to learn mathematical concepts alongside the mathematicians that figured them out!

And speaking of doing the math, right now, the first 200 people to sign up at. Brilliant.org/SciShow will get 20% off an annual Premium subscription! So if you like math and saving money, you'll probably want to head over there soon. [♪ OUTRO].