You can't teach an old dog new tricks, but some scientists hope dogs can teach humans about the process of getting old -- and how, maybe, we can reverse it.
"Dogs are great models for figuring out why humans decline over time," National Geographic contributing writer Fran Smith told ABC OTV.
Smith explored the science behind canine longevity -- and what humans can learn from this research -- for NatGeo's new "Mind, Body, Wonder" series.
For years, scientists were convinced that aging was not reversible. Then, promising studies with simple organisms like worms and fruit flies and later mice produced ample evidence that aging can be delayed and life can be prolonged in these creatures, Smith said.
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Now, in searching for a breakthrough in human life, longevity researchers have turned their attention to dogs.
One reason is simple: Dogs are much larger mammals, more similar to people than worms or rats.
Our shared environments also play a big role.
"They share our food. They are the closest animals to us, lifestyle-wise," Smith said. "We walk them. We walk with them. They're drinking the same water we're drinking ... They're breathing the same air. Any pollution, any environmental factors that impact dog health could also potentially impact our health."
And "dog years" matter.
"You can do studies with dogs and really get answers about the effect on lifespan, life expectancy and longevity in a matter of years, whereas you did the same studies with people, it would take you decades," Smith said.
One ambitious effort, the Dog Aging Project, is examining the "life experiences" of pet pooches over a 10-year period to "identify the biological, environmental, and genetic factors that promote healthy longevity," Smith reported.
A small subset of the more than 40,000 dogs enrolled are undergoing a clinical trial of rapamycin, one of the most promising candidates for a human longevity drug.
"Rapamycin has been used for a long time as a drug for organ transplant patients to prevent rejection," Smith said. "There's really good evidence from mice studies that it can delay aging, and for a long life ... I know some researchers actually occasionally take rapamycin themselves off label because they really believe in it."
Another company has turned to experimenting with gene therapy in pups to promote healthy aging and longer life.
So far, data from dog studies show that if humans want to live longer, diet and exercise matter.
"They have very good evidence that physical activity really is protective against cognitive decline later in life, and another study out of the Dog Aging Project found that one daily meal is better than frequent feeding," Smith said.
But no matter what's learned, mankind wants what's best for its best friend.
"Americans have 77 million dogs," Smith said. "We love our dogs, and any drug, any kind of diet that would help our dogs live better is of great interest to lots and lots of us."
Find out more about these longevity studies and how you can nominate your canine companion to participate in one at NatGeo.com/health.
ABC OTV and National Geographic will explore health and wellness through four lenses: longevity, women's health, brain health, and diet and nutrition. Using the latest in scientific research and information from experts in the medical field, we'll answer questions about what's essential to the future of your health.
The Walt Disney Co. is the parent company of National Geographic Partners and this ABC station.