Humans and dogs have a history that spans back thousands of years. It’s no surprise therefore that we have always compared a dog’s life to our own. A century-old method for comparing dog years to human years states that one dog year is equivalent to 7 human years.
The rationale behind this method of comparing dog years to human years is quite simple. Dogs have an average life expectancy of 10 years while a human’s life expectancy is 70 years.
That said, it’s important to note that the breed of the dog, as well as its size, affects a dog’s life expectancy. For instance, smaller dogs on average live longer than larger breeds. Larger dogs, however, mature much faster during their first few years.
However, a large dog breed puppy might mature faster but may reach senior status at age 5. On the other hand, a small dog breed pup might take longer to mature but reach senior status at age 10. Medium-sized dogs lie somewhere in the middle.
According to the Great Dane Club of America, the life expectancy of the breed is 7-10 years. According to the 1=7 method for converting dog years to human years, a 5-year-old Great Dane is equivalent to a 35-year-old human.
How to tell the age of a dog
You may be looking to adopt your next pup. However, without paperwork, finding out the age of the pup can be a bit of a challenge. Luckily, there are several ways you can tell the age of the dog.
One of the best ways to tell the age of a dog is by checking the teeth. For instance, an 8-week-old pup will have grown all the baby teeth. After seven months all the milk teeth will be replaced by more permanent teeth that look white and healthy.
After about 1 or 2 years, the teeth start to take a duller look and some of the back teeth turn yellow. In 3 to 5 years, the dog’s teeth will have a bit of tartar as well as some wear and tear.
In 5 to 10 years, the dog’s teeth will have more visible wear and tear and a lot more tartar buildup. Likewise, between 10 and 15 years, there will be heavy wear and tear and a lot of tartar buildup. Also, there may be teeth missing in some dogs.
Other signs of aging include grey hair that starts at the muzzle and extends over the dog’s body as they advance in age, as well as loose skin, cloudy eyes, and stiffness in the legs.
The American Veterinary Medicine Association gives a general guideline on how to calculate dog years to human years.
The first year of your dog’s life is equivalent to 15 human years.
The second year of your dog’s life is equivalent to 9 human years.
Any other year after the second year is equivalent to 5 human years.
We’ve noted that smaller sized dogs tend to have a longer lifespan than larger dogs. Some long-living dog breeds include the Maltese, miniature schnauzer, poodle, Boston terrier, shi tzu, dachshund, beagle, Shetland sheepdog, and chihuahua.
The Epigenetic clock study
While there is no doubt on the popularity of the 1 human year equals 7 dog years method of converting dog years to human years, there is another more scientific method known as the epigenetic clock study.
Scientists have discovered that as people advance in age, there are changes in the DNA structure involving the addition of certain specific chemicals to the DNA. Moreover, these chemicals are methyl groups that bind to specific DNA strands as a result of lifestyle, genetics, and disease over the years.
Of course, there is more detail in the study but we are going to lay it down in simple language that is easy to understand. Furthermore, through the study, scientists can identify the age of a person based on the methylated DNA.
But what is the connection with our dog’s age and how can we use the study to compare dog years to human years?
Well, other animals including dogs also undergo methylation in their DNA and therefore have epigenetic clocks.
Scientists discovered that regardless of the breed of dog, all pooches undergo the same process of DNA methylation. In addition, they reached puberty at about 10 months and died before the age of 20. What’s most interesting with the study is that the scientists found that the process of DNA methylation was very similar to humans.
Research has shown that dogs and humans seem to have similar diseases when they age. For example your dog can catch a cold. Consequently, this also means that at a molecular level, both humans and dogs undergo a similar process of aging.
During the epigenetic clock study, the scientists also went a step further to compare the rate of methylation in humans to that in dogs. The scientists came up with a formula which states that a dog’s human age can be calculated by taking the natural logarithm of the dog’s age, multiplied by 16 and added to 31.
The key point to note here is the natural logarithm of the dog’s real age. This simply refers to the logarithm of the dog’s age taken to the base of the constant e, where e is roughly equal to 2.718
The various human life stages seem to match up to a dog’s life stages. Based on the research, a 7-week puppy is the same age in dog years to a 9-month-old human. At that time, both are beginning to grow the first teeth.
Compared to the life expectancy of a human which is 70 years, the data is also in line with a Labrador retriever with a life expectancy of 12 years.
The bottom line is that during the first year of a dog’s life and the first few years of a human’s life, the rate of methylation on DNA in both dogs and humans is slow. However, as they both progress in life, the methylation rate increases. If you’ve been wondering why your pooch sneezes just like you, now you know!