You’ve probably seen it with your own eyes before, but a research team that published its findings in the journal Science says it noticed it at an epigenetic level: big dogs age faster. Chihuahuas, for as obnoxiously yappy as they are, seemed to last forever, while Great Danes, those big lovable galoots, give you about a decade before they cross the rainbow bridge.
Researchers at Arizona State University analyzing DNA from nearly 900 dogs in the Dog Aging Project finally know why big dogs don’t last as long. It all has to do with rogue “jumping genes.”
Scientists Say ‘Jumping Genes’ Could Explain Why Big Dogs Have Shorter Lives
Inside dog DNA, a specific class of “jumping” genes called LINE1s exists. Normally, a biological process called DNA methylation stamps chemical tags onto these genes to keep them locked down, but as big dogs age, that regulatory process falls apart and LINE1s start shaking loose, jumping between chromosomes, shredding DNA apart in the process, thus causing instability in the cells, triggering inflammation and cancer.
This happens to all dogs, but in big dogs it happens catastrophically and early. Giant breeds shed roughly 35 percent more LINE1 methylation per year than smaller dogs that fit in a purse.
Or, to put it less scientifically: there’s just too much dog for their bodies to keep up with. Humans specifically bred big dogs for their rapid growth, but that early growth leads to a genetic mess later in life, as their biological clocks essentially run twice as fast as a smaller dog’s.
The researchers think these out-of-control jumping genes could be a universal mammalian aging mechanism, and that learning more about them could eventually help us learn a little about ourselves, too, since dogs get a lot of the same age-related diseases that we do, largely because we share environments.
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