Science explains why big dogs live shorter lives

Key research from the University of Adelaide has shed light on why dogs Larger dogs (breeds such as the Great Dane) live shorter lives than smaller ones.

Scientists studied the causes of differences in life expectancy and mortality in 164 dog breeds, ranging from Chihuahuas to Great Danes.

“When we analyzed these datasets, we found that larger dogs were more likely to die of cancer at a younger age compared to smaller dogs,” said Dr. Jack da Silva from the UC Adelaide School of Biological Sciences.

“Large dogs don’t necessarily age faster than small breeds, but studies have shown that as the breed’s average body weight increased, so did the incidence of cancer.”

“We think the relationship between dog body size and lifespan may be due to an evolutionary lag in the body’s defense against cancer that cannot keep up with the recent rapid selective breeding of larger dogs,” he said.

Study published in the journal American naturalistfound that a shorter life is consistent with a theory of aging known as life history optimization or “one-time soma”.

“This theory is based on the idea that if you put most of your resources and energy into growth and reproduction, you can’t also put it into cell repair and cancer protection. In all organisms, the focus is on early reproduction, even if it comes at the cost of maintaining and repairing the body and extending lifespan,” Dr. da Silva said.

The results may also be useful in the study of human aging.

“Dogs are a good model for studying human aging. Dogs, like people in industrialized countries, live in an environment that tends to protect them from accidents and infectious causes of death, and so they are more likely to die from age-related diseases such as cancer,” Dr. da Silva said. .

While the results of this survey may be worrisome for owners of large dogs, the researchers predict that larger breeds will evolve to develop better cancer-fighting genes.

“Most of the 400 or so dog breeds that we know about today were bred only in the last 200 years. Larger dogs didn’t have time to develop better cancer defense mechanisms to match their size. It can still happen, but it can affect reproduction,” Dr. da Silva said.

Dr. da Silva predicts that larger breeds will adapt and extend their lives, but according to the theory of aging, they are more likely to have smaller litters in the future.

“This can happen naturally or through selective breeding as people focus on breeding larger dogs with lower cancer rates and therefore longer life spans,” he said.

This study was the result of a year-long comparative analysis using published dog breed data from around the world.