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RandomFactor writes:

Conventional wisdom has long been that one dog year was equal to seven human years. Now it appears that reality is not so simple.

[A] new equation developed to measure how a dog ages finds the family pup may be a lot older than we realize.

Researchers studying chemical changes to canine DNA found that dogs age very quickly during their first five years and much more slowly later on.

The findings, published recently in the journal Cell Systems, calculate that a 5-year-old dog would be pushing 60 in human years.

The new equation is far less intuitive than multiplying by seven: 16 ln(dog age in years) + 31 = human age in years, where "ln" is the natural logarithm function.

Using that equation:

• a 1-year-old dog is like a 31-year-old human;
• a 3-year-old dog is like a 49-year-old human;
• a 7-year-old dog is like a 62-year-old human.

By this time, dog aging has slowed down, so an 8-year-old dog is like a 64-year-old human.

Research was done by comparing methylation marks on dog and human DNA over time.

[M]ethylation marks, or as [Troy Ideker, senior author of the study] calls them 'wrinkles on the genome,' change in predictable ways as we and dogs age.

According Ideker

[The team was] able to quantify this at the molecular level and tell how fast someone is aging, and [...] align it across dogs and humans

The new formula will need additional adjustment for specific breeds as well, for example larger dogs such as Great Danes live shorter lives than smaller dogs.

Journal Reference:
Tina Wang, Jianzhu Ma, Andrew N. Hogan, et al. Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome, CellSystems (2020), doi.org/10.1016/j.cels.2020.06.006

Original Submission