It makes sense that scientists would turn to other species to deepen and expand our knowledge about longevity, for many species have exceptional life spans that make our own seem suboptimal. Among the longest-living animals on Earth is the ocean quahog (Arctica islandica), which can live 500 years. (To help that hit home: The record-breaking quahog studied by scientists in 2007, “Ming,” was born in 1499.) Similarly, the Arctic-dwelling bowhead whale (Balaena mysticetus) can live 200 years, possibly longer. One way that scientists assess the age of bowheads, who were once heavily hunted, is through harpoon tips still embedded in the whales’ blubber; some of the weapon heads extracted date back to the 19th century.
Then there is a species that theoretically can live forever—the “immortal” jellyfish (Turritopsis dohrnii). When this tiny yet remarkable creature is hurt or otherwise in distress, it can essentially age backwards, transforming from the adult or “medusa” stage back to the polyp stage.
Why then are certain species Methuselahs while others, such as mayflies, live for only a few days or even hours? Why does our near relative, the chimp, live in the wild only until the age of 30 or so, while we live more than twice as long? These are critical questions, yet the most important question when it comes to the discovery and development of longevity strategies and interventions for humans is not "Why?" but "How?"
How do long-lived species achieve their years? To answer this and uncover some of the animal kingdom’s longevity secrets, scientists are investigating a range of factors, including cellular maintenance and DNA repair, disease resistance, genetic and epigenetic variations, external factors such as environmental stability, behavioral factors such as reproductive strategies, and more. So far, they’ve only managed to fill in some of the picture. For instance, larger, more energy-preserving animals—think elephants and tortoises—generally have longer lifespans. Additionally, recent studies have shown that inborn defenses such as hard shells and poisons aid longevity in reptiles and amphibians. Research also is being done to understand more about some animals’ ability to suppress cancer. One takeaway is that there are different pathways to a long life.
Sociality research
Another area of study—already heavily investigated in humans—is social organization and sociality. How does longevity compare in social animals compared to more solitary ones?
If you suspect more social types tend to live longer, you’re not alone. Research has shown that more gregarious mammals, for example, have longer lifespans. In January 2023, a study published in Nature discussed a phylogenetic comparative analysis of approximately 974 mammalian species on three states of social organization: solitary, pair-living, and group-living. It found that group-living mammals such as chimpanzees lived longer than solitary ones such as shrews. The longer life spans associated with group living may be due to a lower risk of predation and starvation as well as the benefits of stable, strong social bonds, the researchers said.
“These benefits,” they wrote, “are expected to override the costs inherent in group living, such as competition for mating partners and food, stress from higher-ranking individuals, and the spread of infectious diseases via social contacts.”
The researchers also said that kin selection may be a factor in the correlated evolution of longevity and social structure. That is, how related animals work cooperatively, share duties of raising offspring, disperse to new territories, and create and maintain social hierarchies can help promote longevity.
Who and What
Scientists interested in longevity also ask questions about how to study other species. For a long time, noted science writer Bob Holmes in a May 2021 Knowable article, biomedical researchers tended to study short-lived species such as fruit flies and nematodes. Studying these animals has led to many breakthroughs. They have the advantage of rapid experiments with their short lives and being cost effective to keep, but they may lack many mechanisms that allow for long lifespans in humans. But some scientists are broadening the range of research subjects to include those that can shed light on additional mechanisms and adaptations that promote longevity from the animals that have lived the longest.
Biologist Steven Austad asks a different question in his book, Methuselah’s Zoo: What Nature Can Teach Us about Living Longer, Healthier Lives, published by MIT Press in August. Written in a lively, reader-friendly style, it argues that the best way to glean valuable lessons from other animals is to study them not in the lab but in the wild.
“Might the laboratory of nature, in which some species had evolved to be much more successful than humans at staving off the depredations of aging,” he writes, “have something to teach us that we would never learn from our laboratory bestiary of tiny worms, fruit flies, and domesticated mice?”
There are so many avenues to explore when it comes to longevity, and even questions about questions, but slowly scientists are uncovering the myriad ways some species can live what, to our eyes, are remarkably long lives.