Aging is not for everyone, as studies show

Fabrizio Coffrini A special albinos Galapagos giant tortoise baby, born on May 1, is captured in a photo taken on June 3, 2022, near to its mother at the Tropicarium of Servion, western Switzerland.

Be born a turtle, according to scientists, and you’ll live forever.

A theory of evolution that claims that senescence, or slow physical decline over time, is an inevitable fate has been called into question by two studies that were published in the journal Science on Thursday and found no evidence of aging among some cold-blooded organisms.

According to Penn State wildlife ecologist David Miller, a senior author of one of the papers, although there have been eye-catching individual reports—such as that of Jonathan the Seychelles tortoise, who turns 190 this year—these were considered anecdotal and the issue had not been studied systematically.

However, he added, “a lot of what we knew about amphibians and reptiles were from a species here, a species there.” Researchers have “done a lot more comparative, really complete work with birds and animals in the wild.”

Miller and colleagues used data from 107 populations of 77 species in the wild, including turtles, amphibians, snakes, crocodilians, and tortoises, from long-term field research.

All of these employed a method known as “mark-recapture,” in which a certain number of individuals are captured and tagged, followed over time to see if they can be found again, and researchers then calculate death estimates based on probabilities.

Additionally, they gathered information on the animals’ lifespans after reaching sexual maturity and utilized statistical techniques to calculate longevity, or the age at which 95% of the population is dead.

Beth Reinke, a biologist and the study’s principal investigator from Northeastern Illinois University, said, “We observed evidence of insignificant aging.

Although they had anticipated that this would apply to turtles, it was discovered that one species of each category of cold-blooded animals, including crocodilians, toads, frogs, and toads, shared this trait.

She continued, “Negligible aging or senescence does not imply that they are immortal.” It means that although there is a chance of dying, that likelihood does not rise with advancing age.

In contrast, the chance of death in a year for adult females in the US is approximately 1 in 2,500 at age 10 and 1 in 24 at age 80.

The US National Institutes of Health, which is keen to learn more about aging in ectotherms—cold-blooded species—and apply it to warm-blooded humans, supported the study.

It’s not the metabolism.

Ectotherms, which have lower metabolisms and depend on external temperatures to maintain their body temperatures, are believed by scientists to age more slowly than endotherms, who produce their own heat internally and have greater metabolic rates.

Within animals, this link is real. For instance, mice have a far faster metabolic rate and a much shorter life span than humans.

Unexpectedly, the current study discovered that metabolic rate was not the primary driver as previously believed.

Even after accounting for variables like body size, “there were ectotherms that age quicker and live shorter lives than endotherms, but there were also ectotherms that age slower and live longer than ectotherms.”

Intriguing hints from the study also offered potential directions for further investigation. For instance, the team discovered that warmer reptiles age more quickly when examining average temperatures of a species rather than metabolic rate, whereas the opposite was true for amphibians.

According to one idea, creatures with protective physical characteristics, like turtle shells, or chemical characteristics, like the toxins some frogs and salamanders may release, lived longer and grew older more slowly than animals without those characteristics.

The ability to consume a turtle becomes quite difficult because of its shell, according to Miller.

“What that accomplishes is it allows evolution to work to reduce aging so that if they do avoid getting eaten, they still function well,” said the researcher.

In a second study, 52 species of turtle and tortoise from zoo populations were examined using identical techniques by a team from the University of Southern Denmark and other institutions. They discovered that 75% of the species had minimal signs of aging.

Scientists Steven Austad and Caleb Finch commented in a statement regarding the results, “If certain species truly defy aging, and mechanistic studies may disclose how they do it, human health and longevity could benefit.”

However, scientists did point out that although while certain species don’t see an increase in mortality over time, they do display age-related ailments.

They claimed that Jonathan the tortoise “is now blind, has lost his olfactory sense, and must be fed by hand,” demonstrating how irreparable the effects of time are.