Big dogs age faster than little ones, and scientists now have a molecular explanation. A large study of dog breeds has linked the size-lifespan trade-off to so-called “jumping genes” in DNA.The study, published in the journal Science on Thursday, analysed nearly 900 dogs across about 120 breeds. Researchers found that big dogs accumulate chemical changes to DNA, known as epigenetic changes, at a faster rate than small dogs.The key culprits are LINE1 elements, also called jumping genes.

These DNA segments can copy themselves and move around the genome, causing damage. They are normally kept in check by a chemical mark called methylation. Giant breeds lost about 35 per cent more of this protection per year than small breeds.Male dogs also aged faster at the molecular level than females, the researchers found, even when males had been neutered young.

The work used data from the Dog Aging Project, one of the largest studies of its kind.The findings could help scientists understand ageing in humans too. Dogs share our homes and environments, so lessons from their biology may translate into better care for both species.