Aging

One Dog Year Doesn't Equal Seven Human Years

Here at Curiosity, we have a rule of thumb we like to throw around: if the idea has the number three or seven in it, chances are it's a myth. Celebrities don't really die in threes, for instance, and your body doesn't really replace itself every seven years. For whatever reason, those are nice round numbers that people love attaching to nonsense. So when people say that one dog year is equivalent to seven human years, that ought to activate your baloney detector. The truth is that dogs are much more complex than that.

Time Travel, Canine Style

It's tricky to pinpoint exactly where this rule got started. Different points in history calculate the human-dog age ratio differently: a 13th-century inscription at Westminster Abbey put it at 9-to-1, saying that dogs live nine years and humans live about 80. The 18th-century French naturalist Georges Buffon put it at 9- or 10-to-1. At some point, someone probably reckoned that the average human lived for 70 years and the average dog lived for 10, and the classic rule about dog years was born.

But think about it: dogs are able to reproduce at one year of age, and some live 20 years or longer. if one human year were equivalent to seven dog years, then humans would be having babies at age 7 and the oldest of us would be pushing 150. To muddy the waters even more, not all dogs have the same lifespan: small dogs are considered elderly at around 11 years, while giant breeds reach old age around their 7th year. There isn't one ratio that works for all breeds.

How Old Is That Doggy In The Window?

In 1953, French researcher A. Lebeau got to the bottom of this conundrum. He looked at the lifespans of dogs and humans and divided them up by certain life milestones: when they reach puberty, when they reach adulthood, and the maximum years they live. He figured out that dogs don't age in parallel with humans; instead, they age much more quickly at first, then a little less quickly later on. His calculations found that a one-year-old dog is equivalent to a 15-year-old human, a two-year-old dog is equivalent to a 24-year-old human, and then every year after that is equivalent to four or five human years. Of course, this still varies by breed and weight, but it's a slightly more accurate measure than the old seven-year myth.

As for your dog? There are online calculators you can use to figure out Rover's age in human years that take his size into account. But we recommend cherishing the time you've got now, and just living in the moment. They do, after all.

If you'd like to give your pup a head start, check out "The Art of Raising a Puppy." The audiobook is free with a trial of Audible, and any purchases you make from this link help support Curiosity.

Animal Myths Busted!

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Key Facts In This Video

  1. Smaller dogs age less every calendar year than larger dogs, whose lifespans are typically shorter. 00:34

  2. Camels store fat, not water, in their humps. 01:34

  3. Elephants are not afraid of mice, though their poor eyesight means that can be startled by quick movements from any animal. 02:34

Written By
Ashley Hamer
February 1, 2016