dog years. An equivalency of years based on the relative life-spans of dogs and humans. This is a mildly fascinating concept, based on an if you-were-a-dog or if-your-dog-were-human, then how-old-would-you/your-dog be?

The calculation is typically done on the basis of seven to one, the premise being that the average life span of a human is seven times that of the average life-span of a dog. Of course, the “average life span” of a human is not exactly evenly distributed, nor is it a fixed number. Is it based on the figures for human men or human women? Are we speaking of the life expectancy of those in the so-called developed countries, or those in the global south? Perhaps those doing the calculation use the psalmist's three score and ten? In any case, this level of assumption is rarely examined. The life expectancy for dogs appears to be even less considered and even more variable than that of humans. As you can see in the following chart adapted from the work of Fred L. Metzger, DVM, life expectancy appears to drop in an almost direct proportion to the weight of the canine in question. On second thought, maybe that is not so different than in humans.

As I said, the concept is mildly fascinating.

Okay, so it is probably only truly interesting if you are enamored of dogs. What is fascinating is that the concept is widely known and used. Children will proudly figure your dog age for you as if they were performing a demanding magic trick. Nobel Prize winning authors name their books Dog Years. Dogs, as they often do, provide a familiar reference point, if not necessarily a comfortable one. As Patrick Martin notes in his poem, “In Dog-Years,” sometimes this idea only serves to remind us that “Humans live long in proportion to what they don't do.”

About the illustrations: Figure 1: I'm 54...In dog years I'm dead. I made this animation to show what I am (or am not) doing in my life. The calendar illustration is a clip from one of the famous card playing dog paintings by Cassius Marcellus Coolidge.

Figure 2 is the cover of Mark Doty's Dog Years. This image is of a book cover, and the copyright for it is most likely owned either by the artist who created the cover or the publisher of the book. It is believed that the use of low-resolution images of book covers to illustrate an article discussing the book in question qualifies as fair use under United States copyright law.