If you live with a dog you are likely aware of the well-known ”rule of paw”: one dog year is the equivalent of 7 human years. Now scientists say that formula is wrong. Dogs are actually much older than we previously estimated. Researchers have devised a more accurate formula to calculate a dog’s age based on the chemical changes in the DNA as organisms grow old.
Like humans, dogs follow similar developmental trajectories that lead them to grey and become more susceptible to age-related diseases over time. However, how they age on a molecular level is more complicated — aging rapidly at first and slowing down later in life…
Human and dog DNA, which codes who we are, doesn’t change much throughout the course of life, but chemical marks on the DNA, called ‘methylation marks’, do. Scientists consider these marks like wrinkles in the genome.
“It is very much like when you look at someone’s face and guess their age based on their wrinkles, gray hair, and other features. These are just similar kinds of features on the molecular level.”
-Dr. Trey Ideker, researcher, University of California, San Diego
With the help of two canine experts, researchers studied 104 Labrador retrievers spanning from few-week-old puppies to 16-year-old dogs. The comparison revealed a new formula that better matches the canine-human life stages: human age = 16 years ln [natural logarithm] (dog age) + 31. Based on the new function, an 8-week-old dog is approximately the age of a 9-month-old baby, both being in the infant stage where puppies and babies develop teeth. And a 6 year-old dog is biologically pushing 60 years of age. The average 12-year lifespan of Labrador retrievers also corresponds to the worldwide life expectancy of humans, 70 years.
Remember that the next time you think about pushing your 8 year-old dog to keep up with you on a long hike.
Journal Reference: Tina Wang, Jianzhu Ma, Andrew N. Hogan, Samson Fong, Katherine Licon, Brian Tsui, Jason F. Kreisberg, Peter D. Adams, Anne-Ruxandra Carvunis, Danika L. Bannasch, Elaine A. Ostrander, Trey Ideker. Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome. Cell Systems, 2020; DOI: 10.1016/j.cels.2020.06.006
NIH researchers reframe dog-to-human aging comparisons
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