Life, for most of us, ends far too soon—hence the effort by biomedical researchers to find ways to delay the aging process and extend our stay on Earth. But there's a paradox at the heart of the science of aging: The vast majority of research focuses on fruit flies, nematode worms and laboratory mice, because they're easy to work with and lots of genetic tools are available. And yet, a major reason that geneticists chose these species in the first place is because they have short lifespans. In effect, we've been learning about longevity from organisms that are the least successful at the game.
Today, a small number of researchers are taking a different approach and studying unusually long-lived creatures—ones that, for whatever evolutionary reasons, have been imbued with lifespans far longer than other creatures they're closely related to. The hope is that by exploring and understanding the genes and biochemical pathways that impart long life, researchers may ultimately uncover tricks that can extend our own lifespans, too.
Everyone has a rough idea of what aging is, just from experiencing it as it happens to themselves and others. Our skin sags, our hair goes gray, joints stiffen and creak—all signs that our components—that is, proteins and other biomolecules—aren't what they used to be. As a result, we're more prone to chronic diseases such as cancer, Alzheimer's and diabetes—and the older we get, the more likely we are to die each year. "You live, and by living you produce negative consequences like molecular damage. This damage accumulates over time," says Vadim Gladyshev, who researches aging at Harvard Medical School. "In essence, this is aging."
This happens faster for some species than others, though—the clearest pattern is that bigger animals tend to live longer lives than smaller ones. But even after accounting for size, huge differences in longevity remain. A house mouse lives just two or three years, while the naked mole rat, a similar-sized rodent, lives more than 35. Bowhead whales are enormous—the second-largest living mammal—but their 200-year lifespan is at least double what you'd expect given their size. Humans, too, are outliers: We live twice as long as our closest relatives, the chimpanzees.
Perhaps the most remarkable animal Methuselahs are among bats. One individual of Myotis brandtii, a small bat about a third the size of a mouse, was recaptured, still hale and hearty, 41 years after it was initially banded. That is especially amazing for an animal living in the wild, says Emma Teeling, a bat evolutionary biologist at University College Dublin who coauthored a review exploring the value of bats in studying aging in the 2018 Annual Review of Animal Biosciences. "It's equivalent to about 240 to 280 human years, with little to no sign of aging," she says. "So bats are extraordinary. The question is, Why?"
1.) Sarah J. Mitchell, Morten Scheibye-Knudsen, Dan L. Longo, et al. Animal Models of Aging Research: Implications for Human Aging and Age-Related Diseases*, (DOI: 10.1146/annurev-animal-022114-110829)
2.) Emma C. Teeling, Sonja C. Vernes, Liliana M. Dávalos, et al. Bat Biology, Genomes, and the Bat1K Project: To Generate Chromosome-Level Genomes for All Living Bat Species, (DOI: 10.1146/annurev-animal-022516-022811)
Zhonghe Ke, Pramit Mallik, Adam B. Johnson, et al. Translation fidelity coevolves with longevity [open], Aging Cell (DOI: 10.1111/acel.12628)