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When calculating your dog’s age, a common rule of thumb for pooch owners has always been that one year for dogs is equivalent to seven human years. New research now suggests you can bury that bone of thought for good. The math isn't quite that simple.

Scientists believe that the first year of your dog’s life is actually equal to about 15 human years. Just more reason to spend every second you can with your dog. Because the clock is ticking so quickly, there’s simply no time to be unhappy!

Researchers at the University of California San Diego School of Medicine have developed a new formula for determining your dog’s “real age”. Led by Trey Ideker, professor of medicine and bioengineering, the formula goes a long way in explaining why some dogs want to chase balls with child-like eagerness while others prefer loafing all day on a recliner (belly rubs mandatory). It all boils down to what stage of life they're really in.

By tracking molecular changes in the DNA of Labrador retrievers, and in particular "the changing patterns of methyl groups" in their genome, researchers have determined that dogs age at a much faster rate than humans early in their lives, then slow down after reaching maturity.

"This makes sense when you think about it - after all, a nine-month-old dog can have puppies, so we already knew that the 1:7 ratio wasn't an accurate measure of age," Ideker said. “Based on the study, a one-year-old dog compares to a 30-year-old human, a four-year-old dog to a 52-year-old human. The rate of aging decreases after dogs turn seven.”

For those of us who flunked maths in school (hands up), crunching the numbers may be a little confusing. So we’ll simplify it further (best you grab a calculator).

Dogs live an average of 12 years – give or take, depending on their breed size. Large and giant breeds are usually considered to be seniors by the time they’re five, while medium-sized dogs won’t reach old age until they’re seven. Small and toy breeds reach their golden years around the age of 10. Life expectancy in humans, by contrast, is at least five times that. To come up with a better formula for comparing human and dog ages, Ideker's team looked at chemical markers in the DNA of 104 Labradors ranging from just weeks old to 16 years old.

“Although an animal's DNA does not change during its lifetime, these chemical markers - called methyl groups - do. As the years pass, methyl groups accumulate in the DNA, causing certain genes to turn on and off. After tracking how these groups accumulate in different parts of Labrador genomes over time, we compared that accumulation rate to the same methyl group changes in humans,” explained Ideker.

“We found that in a dog's first year of life, the animal accumulates more methyl groups than a human does. So an eight-week-old puppy, for example, is equivalent to a nine-month-old baby. Then, as the years pass, that accumulation rate slows down in dogs to better match the accumulation rates of humans."

The short end of the tail is that older dogs age more slowly once they get older.

So how old is your dog, really? To work it out yourself, you need to multiply the natural logarithm of a dog's age by 16, then add 31 – that will give you the equivalent in human years. Find your dog's age along the bottom axis of the graph we've included and trace your finger straight up until you reach the red curve. Then trace your finger straight over to the left to find the corresponding human age. Essentially, for each year older a dog gets, the corresponding increase in "human years" gets smaller and smaller. So based on that formula, a six-year-old lab is 60 human years old. But a 12-year-old lab is 70 human years old.


According to The Book of Times: From Seconds to Centuries, a Compendium of Measures by Leslie Alderman, most of us spend just forty minutes or less a day with our pets.

“That’s quite tragic, especially when we know how little time we really have with our dogs,” said Network for Animals (NFA)’s executive director David Barritt. “If there’s one thing we could all use a little bit more of, it’s time with our pets. While we can’t turn back the clock, or fill their drinking bowls with water from the fountain of youth, we can cherish every second we have with them and make the very most of their time with us. Dog’s lives are short, so make sure your dog has its day – every day.”


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