Growing old is a fact of life – well, apparently not if you are a turtle. Evidence collected across two new studies reveals that several turtle species experience very little senescence, what we technically call the physical aging of our bodies. Turtles appear to escape the weakening and deterioration of age.
The ability to slow down and even switch off senescence has been seen in Testudines, the order of reptiles encompassing turtles, terrapins, and tortoises. One famous example is Jonathan, the world’s oldest living land animal who at 190 years of age continues to enjoy sex with his male and female companions, showing little sign of age.
In one of the new studies, published in the journal Science, the team used the data from several long-term field studies that focused on 77 species from 107 wild populations. These included not just turtles and tortoises, but also amphibians, snakes, and crocodilians.
These cold-blooded animals showed a greater diversity of aging rates compared to birds and mammals, and they believe that in the case of the turtles their bony shell and slow pace of life (following the first reproduction) can help explain why they age so slowly – or not at all.
“These various protective mechanisms can reduce animals’ mortality rates because they’re not getting eaten by other animals. Thus, they’re more likely to live longer, and that exerts pressure to age more slowly. We found the biggest support for the protective phenotype hypothesis in turtles. Again, this demonstrates that turtles, as a group, are unique,” lead author Beth Reinke, assistant professor of biology at Northeastern Illinois University, said in a statement.
While being cold-blooded doesn’t guarantee a lack of aging, the team found at least one species with little to no senescence in every group including, frogs and toad, crocodilians, and obviously turtles.
“It sounds dramatic to say that they don’t age at all, but basically their likelihood of dying does not change with age once they’re past reproduction,” said Reinke.
According to the second study, also published in Science, better environmental conditions equate to even slower aging. They looked at 52 turtle, terrapin, and tortoise species in zoo populations, and found that 80 percent age slower than modern humans – and 75 percent have slow or negligible senescence.
“Contrary to widespread theories of aging, we show that many species of turtles and tortoises have found a way to slow down or even completely switch off senescence. This means that senescence is not inevitable for all organisms,” lead author Rita da Silva, who was at the University of Southern Denmark when the work was done, said in a statement.
For humans, the likelihood of dying before your next birthday is about 1 in 1,000 in your 30s and then grows larger and larger as you grow older – but not for these animals, their risk of death doesn’t change. Sure, they can still succumb to diseases, accidents, or predators, but their likelihood is the same at 10 and at 130. In the case of the Black Marsh turtle, their risk of death actually decreases with age.
There are studies investigating if it's possible to slow down senescence in humans as well, with promising results found in mice.