I have always been told that one human year equals seven dog years. So, my four-year-old Labrador would really be 28 years of age, while my 10-year-old Jack Russell would be 70 years old. How accurate is that belief?
While it is a commonly-held belief that one human year is equivalent to seven dog years, it is not quite that simple. Humans do age slower than dogs, but not seven times slower. If that were the case, we would be able to have children of our own by the age of seven and live over a century and a half! One of the key differences between dogs and humans is that dogs reach sexual maturation within the first 12 months of life, and will age much faster during those first two years then we will during our first two years as humans.
Science behind how and why dogs age differently has progressed greatly over the last decade, most notably centered around the concept that as an individual ages, their DNA goes through chemical modifications known as an epigenetic clock. By converting information regarding this DNA methylation status into an age estimate, scientists are better able to predict how long an individual will live. This information is being applied toward more accurately charting a dog or a human’s expected lifespan.
Size also has an impact on the average lifespan. Smaller dog breeds age slower than their larger counterparts, so your Jack Russell is more likely to have a longer lifespan than your Labrador. Giant breeds such as Great Danes have unusually short lifespans due to their massive size. In general, the larger the dog, the harder their organs – most notably their hearts – have to work. This, combined with genetic predisposition for inherited heart diseases, gastric dilation, bone and joint diseases and thyroid issues result in the average lifespan of a Great Dane to be around eight to 10 years.
As a canine behaviorist, I am fascinated by the connection between mankind and dogs. It is often wondered in the scientific community why our ancestors chose to spend the majority of our lives alongside an animal with such a dissimilar lifespan. The average person will own five to six dogs in their lifetime, usually starting in childhood with a beloved family pet, and culminating with a companion in their later years. Why not choose the elephant with a 70-year lifespan? Or a sea turtle or a macaw? Why are dogs so beloved by ancient and modern mankind alike, when they live a fraction of our lives?
One argument is that we chose to create the grand species of dogs from the humble wolf due to their size. It is not practical to share your living room with an elephant. The size and shape of the average dog makes them ideal companions for our everyday lifestyle. They are not protected by a shell – as a sea turtle is – or slimy as a snake. They are comfortable to lean against, pleasant to pet and have comprehensive physical traits – paws to our feet and hands, the same number of heads and eyes. It can be difficult to feel completely compatible with an animal that expresses themselves with hissing, clicks or echolocation. Dogs bark, howl, chatter their teeth, huff and sigh, wrinkle their noses, slink, stretch, dream and share very similar expressions with us, thus allowing us to empathize with them more easily.
It’s not just that dogs are physically pleasing to interact with. Their brains are also compatible with our own. Numerous scientific studies have proven that when dogs and humans interact with one another, both partners experience a large dump of oxytocin. Oxytocin is a hormone which promotes a sense of general wellbeing, enjoyment and love. When you pet your dog with meaningful, gentle touch, your brain and theirs releases this potent hormone, resulting in a sensation of care and increased bond.
Our dogs’ brains also react to the sound of voices the same way ours do. High pitched, emotionally charged sounds such as a baby crying, laughing or shrieking caused similar responses. This is why dogs are so in tune with us and can mirror our emotional states so accurately. When you feel sad and speak in low, upset tones, your dog perceives your distress as accurately as a fellow human might. And, do you know that inquisitive, interested look your dog does when you ask a question? Dogs have even evolved muscles around their eyes which allow them to mimic an “infant like” expression which prompts their human companions to feel a “nurturing response.” We really did co-evolve as two species!
So, how old are your dogs? There are many online resources and charts to help you estimate this, but the one I often turn to is based on the studies on the epigenetic clock that results from aging. Per that study conducted by the geneticist Trey Ideker of the University of California, San Diego, your two-year-old Labrador would be 53 and your 10-year-old Jack Russell would be 67. I hope this answered your question and that you learned some interesting facts about mankind’s best friend!
Kendall and Chandler Brown are owners of Custom K-9 Service Dogs, a dog training business serving Minden/Gardnerville, Carson and Reno. For information go to customk9servicedogs.com or email email@example.com.
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