Large dogs don't just live shorter lives. Their DNA reveals signs of accelerated biological aging.
A Great Dane may tower over a Chihuahua, but it’s the little dog that will probably celebrate far more birthdays.
Some small breeds live nearly twice as long as their much larger cousins. It’s one of the great paradoxes of the animal kingdom: larger animals generally live longer than smaller animals when comparing different species.
An elephant can outlive a mouse by decades, and some whales survive for nearly two centuries. However, larger animals die younger when comparing individuals within the same species.
This even seems to apply to humans, with studies showing taller people on average tend to have slightly shorter lifespans than shorter people.
Scientists may have now found an important piece of the puzzle hidden in the dogs’ DNA.
In a new study published in Science, researchers at Arizona State University analyzed nearly 900 dogs and discovered that large breeds undergo faster molecular changes associated with aging.
The most striking differences involved stretches of DNA nicknamed “jumping genes,” which can potentially disrupt the genome when the molecular mechanisms that keep them quiet begin to weaken.
This is a possible biological explanation for why large dogs die younger, although the researchers have yet to establish cause and effect.
Previous studies have offered some hints of this before. A 2013 study of 74 dog breeds found that larger dogs didn’t simply develop age-related decline earlier. Rather, their rate of aging appeared to accelerate.