If dogs and humans both have a heart and things we need to survive, then why don’t dogs live as long as humans? The main reason people used to think big animals live longer is because of something called metabolic rates. www.shutterstock.comWe want to know how to help dogs live longerThere is a lot of scientific research on why dogs age and how to help them live longer. This is partly because we love dogs, and partly because learning about them can help us figure out how humans can live longer too. Scientists have found that although dogs don’t live as long as we do, their life expectancy (how long they live) has doubled in the last 40 years.