A Popular Science View of Negligible Senescence in the Animal Kingdom

Some animals, even mammals such as the naked mole-rat, show few signs of degenerative aging across a life span, a state known as negligible senescence. Such species typically live considerably longer than their more evidently aging near relative species. There isn't any one path to negligible senescence, as demonstrated by the wide variety of ecological niches containing species found to be negligibly senescence. Can we learn from their biochemistry to find ways to meaningfully extend the healthy human life span? Undoubtedly so in the very long term, at the point at which the cutting edge of research is building entirely new higher animal genomes with confidence, but it is too soon to say whether any of the novel age-slowing and age-reversing therapies of the next few decades will be informed by an improved understanding of the comparative biology of aging.

Theoreticians in the 1960s who were trying to wrap their heads around the principles of why and how animals on this planet age argued that senescence is "inevitable." As time goes by, organisms grow old, and their probability of dying increases. But research into a wide range of organisms suggests this almost definitely isn't the case: there's a growing variety in how creatures grow old. On all branches of the evolutionary tree, some animals live fast and die young and those that are so old we don't even know how to measure their age.

Female sand-burrowing mayflies have about five minutes to two hours to mate before they die. Giant Sunda rats live about half a year, while the Rougheye rockfish can live over 200. While many evolutionary principles behind this baffling discrepancy have started to surface, the molecular and biological reasons for aging - and why different animals do it at different rates - still baffles scientists daily. From an evolutionary perspective, however, it is possible to retroactively notice some patterns about what factors might have put these animals in their position on the spectrum.

In general, the bigger you are, the harder it is for another animal to kill and eat you. This is one of the hypotheses for why animals like the bowhead whale - the longest-lived mammal on the planet, sometimes reaching ages of up to 200 years - lives for so long: they don't have many predators out to get them. Elephants also live long for similar reasons, and the size factor would also explain why animals like mice, rats, and voles are so short-lived. They're an easier snack. Bats, though, are tiny, yet one of the longest-lived mammals, too - reaching 40 years old. From an evolutionary perspective, it doesn't matter that they're so tiny, because they're still really good at escaping predators.

There's some evidence that Greenland sharks can live up to 500 years, as can the ocean quahog. They live in extremely icy Arctic ocean environments, which is often associated with slow metabolism and maturation and correlates with living longer. Animals living and evolving in environments that allow them to escape mortality also easily preserve their longevity. Take the Galapagos tortoise. They live on an island and don't have natural predators, so they can take longer to reproduce and grow older - even past 150. Animals with the longest lifespans are often characterized by unique adaptations, habitat, and evolutionary factors that allow them to live for extended periods.

Link: https://www.discovermagazine.com/the-sciences/negligible-senescence-why-do-some-animals-age-differently