Scientists have explained for the first time because the dogs larger dogs have a shorter life expectancy than smaller dogs.
They conclude that selective breeding for size has made large breeds more susceptible to cancer.
Experts from the University of Adelaide, in Australia, examined the causes of differences in life expectancy and death in 164 breeds of dogs, ranging from Chihuahuas to Great Danes.
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“When we analyzed these data sets, we found that larger dogs were more likely to die from cancer at a younger age compared to smaller dogs,” Dr. Jack da Silva of the School of Sciences said in a statement. Biologicals from the University of Adelaide.
“Larger dogs didn’t necessarily age faster than smaller breeds, but the research showed that as the average body weight of the breed increased, so did the cancer rates.”
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“We think the relationship between a dog’s body size and lifespan may be due to an evolutionary lag in the body’s anti-cancer defenses, which cannot keep up with the recent rapid selective breeding of larger dogs. “, said.
The study, which was published in The American Naturalist, found that the shorter life expectancy was consistent with a theory of aging known as life-history optimization, or “disposable soma.”
“This theory is based on the idea that if you invest most of your resources and energy in growth and reproduction, you cannot also invest them in cell repair and defenses against cancer. In all organisms, the focus is on early reproduction, even if it comes at the expense of maintaining and repairing the body and living longer,” Dr. da Silva said.
The results could also be useful when looking at aging in humans.
“Dogs represent a good model for studying aging in humans. Dogs, like humans in the industrialized world, live in an environment that tends to protect them from accidental and infectious causes of death and are therefore more likely to die from age-related diseases such as cancer,” said Dr. da Silva.
Although the results of this survey may be worrisome for large dog owners, researchers predict that larger breeds will evolve to develop better cancer-fighting genes.
“Most of the 400 or so dog breeds we know of today only became established in the last 200 years. Larger dogs haven’t had time to develop better defense mechanisms against cancer to match their size. This could still happen, but it may come at a cost to reproduction,” Dr. da Silva said.
Dr. da Silva predicts that larger breeds will adapt and extend their lifespan, but according to aging theory, they are more likely to have smaller litters in the future.
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“This can occur naturally or through selective breeding, as people focus on breeding larger dogs that have lower cancer rates and therefore longer longevity,” he said.
This research was the result of a year-long comparative analysis study using published data on dog breeds from around the world.
Dr. da Silva is currently investigating the connection between litter size, cancer rates, and life expectancy in dogs and other mammals.
EUROPA PRESS