Scientists knew that dogs were breed for different tasks, but new research shows that traits like activity or aggression needed for those tasks may influence a dog’s lifespan – a finding that may be key in unlocking the mysteries of our own lifespan.

By domesticating dogs, humans unwittingly initiated an artificial selection experiment on personality – the results of which may have implications for our own longevity.

We know that dogs were breed to specific tasks and that individual dogs were selected for reproduction based on certain behavior traits – such as activity, aggressiveness, and docility – related to those tasks.  Today those traits are recognized at dog shows by categories like Sporting, Working, Herding, and Toy and dogs within those categories are recognized for their skills at retrieval, guarding, herding, and human companionship.

But it’s assumed that other traits, such as longevity or energy expenditure were probably not targeted for selection.  Now researchers are finding correlations that suggest metabolism and lifespan changed as by-products of selection on personality traits.  These connections between behavior, metabolism, and longevity have resulted in a “pace-of-life” syndrome hypothesis.

A team led by Vincent Careau, a PhD student at University of Sherbrooke, gathered data on many aspects of dog biology published in such disparate fields of study as psychology, longevity, and veterinary research. While the information was well known within the respective research domains, it was never put together. By combining findings, the authors show that obedient breeds — on average — live longer than disobedient breeds, but aggressive breeds have higher energy expenditure.  As the late naturalist Don Thomas said, “It is hard to imagine how an aggressive personality could be adaptive if it lacked the energetic and metabolic machinery to back up the threats. Simply put, 100 pound weaklings don’t kick sand in weight-lifters’ faces and survive in nature.”

This study, published in the June 2010 issue of the American Naturalist, is significant because it contributes to the growing body of research that shows that personality is related to many crucial aspects of an animal’s life – including energy needs, growth rate and lifespan.  It also brings scientists a step closer to understanding evolutionary causes and consequences of different personality types and may someday be a key in unlocking what determines our own lifespan.