Some Animals Don’t Get Weaker With Age

Some animals actually get more fertile and less prone to dying as they hit their upper years

Photo: Ronn Aldaman

The process of aging feels like a universal truth—everything will, eventually, wane. Sure, you're getting wiser, but then your knees start to go. All of a sudden, it's time for hot flashes and supportive socks. But a study published this week casts doubt on that view. In an analysis of 46 different species from across a range of lifeforms, from mammals to plans to algae, scientists found that not all of the Earth's creatures grow weaker with age.

To figure out how different creatures age, the scientists, led by Owen Jones, looked at how their fertility and mortality rates changed with time. Some animals, like humans, get less fertile and more prone to dying as we get older. Some, like hermit crabs and abalone snails, remain unflinchingly fertile and vibrant all through their days. Some animals, such as desert tortoises, actually become less likely to die as they get older—that is, once they've made it through the dangerous early years, it's pretty much clear sailing.

Lest you think this is just a trick of demographics, where lots of tortoises die as babies, skewing the statistics, the researchers were only focusing on mortality rates after the plants and animals had reached sexual maturity.

Jones et al.:

For some of these species, mortality levels off at advanced ages (for example, for the collared flycatcher, icedula albicollis, the great tit, Parus major, the fruitfly, Drosophila melanogaster) and in others remains constant at all adult ages (for example, for Hydra magnipapillata). For hydra in the laboratory, this risk is so small that we estimate that 5% of adults would still be alive after 1,400 years under those controlled conditions.

According to Nature, the aging style a plant or animal has doesn't depend on how long they tend to live. It's not as if all long-lived species, like tortoises or trees, get stronger with age, while flies burn out quickly.

What this research actually means, in terms of understanding of life as we know it, says Nature, isn't so clear. But one thing is—being a tortoise would be pretty great. (Unless humans have something to do about it.)

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