To understand human longevity, look to the animal world, says James Carey, a biodemography specialist at the University of California, Davis. Studying other species, from insects to elephants, “provides important information for why we age and why we live as long as we do,” Carey says.
By looking at how long other organisms can live, Carey and other researchers have found some guiding principles for why some species flash in and out in days and others live for more than a century. For example, most groups of related organisms have similar maximum known life spans, Carey notes. Songbirds, such as the Eastern bluebird, generally live a maximum of eight to 10 years, for instance, while parrots (African gray parrot shown above) or raptors can survive for decades. Species can evolve so that they live a bit less or more than closely related species, but you probably won’t find a species of mouse that lives 100 years or a tortoise that dashes through life in a month