Dogs go through stages in their life, just as people do, as is obvious to anyone who has watched their stiff-legged companion rouse themselves to go for one more walk.

Poets from Homer to Pablo Neruda have taken notice. As have folk singers and storytellers. Now science is taking a turn, in the hope that research on how dogs age will help us understand how humans age. Like the poets before them, scientists are finding parallels between the two species.

Their research so far shows that dogs are similar to us in important ways, like how they act during adolescence and old age, and what happens in their DNA as they get older. They may be what scientists call a "model" for human aging, a species that we can study to learn more about how we age and perhaps how to age better.

Most recently, researchers in Vienna have found that dogs' personalities change over time. They seem to mellow in the same way that most humans do. And some dogs —like humans — are just born old, which is to say, relatively steady and mature.

Another paper came to the conclusion that the calculus of seven dog years for every human year isn't accurate. You must now multiply the natural logarithm of a dog's age in human years by 16 and then add 31. Is that clear? For example the natural log of 6 is 1.8, roughly, which, multiplied by 16 is about 29, which, plus 31, is 60.

To come to those conclusions researchers sought patterns of chemical changes in DNA, a process called methylation that doesn't alter genes but does change how active they are.

Dogs make a good animal to get results about aging that will help people because they suffer similar ailments, such as “obesity, arthritis, hypothyroidism, and diabetes.” Researchers in Vienna also found that dogs’ personalities change the way that humans’ do. Said one researcher: “People with more mature personality profiles change less as they age. And we found exactly the same in the case of dogs.”

Lab tests can tell how old a human is just from the pattern of methylation. The same can be done for dogs (although they were not tested in labs but blood was taken with the permission of their owners.) The results will help researchers studying aging in dogs to translate findings to humans.

Scientists are unsure about whether the physical decline seen in aging in dogs and humans, in fact in all mammals, is related to the process of development in earlier life or whether the decline is a different process. The researchers said the pattern of methylation suggested that the same genes may be involved in both processes.

As the Dog Aging Project, which is collecting genetic data from pet dogs, puts it: "Longer, healthier lives for all dogs … and their humans."

In, 2018 the co-director of the project, Daniel. E. L. Promislow at the University of Washington, Seattle, laid out the reasons dogs make a good animal in which to study aging and get results that will help people. In essence, they suffer similar ailments, such as "obesity, arthritis, hypothyroidism, and diabetes." And when we imagine that an old dog walks funny for the reasons we do (it hurts), we're not being anthropomorphic.

Elinor Karlsson at the Broad Institute said, "One of the things that we're really interested in is figuring out, first of all, whether there are things in the DNA of dogs that you can find that actually explain why some of them live a remarkably long time." Those findings might be of use in extending healthy aging in people.