TURTLES CAN ALMOST STOP AGEING – WHY CAN’T WE?
Researchers studying slow-ageing animals are beginning to understand why these creatures are able to live longer than us
Some cold-blooded animals can slow their ageing so much that they’re essentially not ageing at all, according to the findings of the most comprehensive study of ageing to date.
Published recently in the journal Science, the study was carried out by an international team of 114 scientists at Penn State and Northeastern Illinois University and involved 77 species of reptiles and amphibians. The team hopes that by studying these animals they can gain insights that could lead to treatments for age-related conditions in humans.
During the study, the team found evidence that turtles, crocodiles and salamanders all aged so slowly that their lifespans are longer than would be expected for animals of their sizes. In fact, some turtles aged so slowly that the team concluded they experienced ‘negligible ageing’, where their bodies don’t age as they grow older.
This doesn’t mean the turtles are immortal, only that their chance of dying isn’t related to their age – unlike in humans, where our likelihood of dying increases the older we get.
“Negligible ageing means that if an animal’s chance of dying in a year is 1 per cent at age 10, if it’s alive at 100 years, its chance of dying is still 1 per cent,” said Prof David Miller, an author of the new study. “By contrast, in females in the US, the risk of dying in a year is about 1 in 2,500 [0.04 per cent] at age 10 and 1 in 24 [around 4 per cent] at age 80.”
The team also found that animals with built-in physical or chemical protections, such as hard shells, tough spines, or venomous bites, aged more slowly and lived longer than animals that didn’t. As these features affect an animal’s chance of dying, they likely influenced how the species evolved.
“Some turtles aged so slowly that they experienced ‘negligible ageing’”
“For the species we looked at, having protective adaptations, being larger and taking longer to mature are all characteristics of species that age slower,” said Miller. “These [traits] all affect mortality, and likely shape how evolution selects for physiological adaptations [in the animal] that limits ageing.”
While these characteristics offer animals protection from predators, they can’t always safeguard against threats like climate change and habitat loss. An animal’s longevity can have other advantages, however, such as helping them endure and overcome challenges.
For example, one species in the study was shown to grow more slowly during hard times. The western terrestrial garter snake, Thamnophis elegans, was able to slow its growth when food supplies were unreliable.
“This allows them to weather droughts that reduce the availability of their prey,” said Miller.
Understanding the evolution and impact of protective traits in animals could bring us closer to understanding human ageing, and point towards new treatments and medicines for ailments related to the ageing process.
“We believe that turtles and other slow-ageing reptiles can be a model for learning about the physiological and genetic processes that underlie ageing [across all animals],” said Miller. “Turtles and some of the longer lived reptiles we studied share some characteristics with humans. Like humans, they take a long time to mature, their external sources of mortality are lower than most species and they’re long lived.”