The Longevity Code: Galapagos Giant Tortoises and Mountain Marmots

While you probably haven’t celebrated it for the past 20 years, World Turtle Day is coming up on May 23. This annual event was created by the American Tortoise Rescue in 2002 to call attention to the dwindling numbers of these animals due to environmental hazards and human interference. It’s also hoped that the occasion will remind people of the joy that seeing tortoises and turtles in the wild can bring and be used to educate people about how we can protect the habitats of such reptiles.

All tortoises are, in fact, turtles; that is, they belong to the order Testudines—meaning reptiles having bodies encased in a bony shell—but not all turtles are tortoises. The main difference between tortoises and turtles is that turtles are mostly found in the water, while tortoises live only on the land, inhabiting deserts, grasslands and wet, tropical forests. Turtles have streamlined and mostly flat shells and can live up to the age of 40. On the other hand, tortoises have larger, more domed shells and live up to 100 years or more. One Seychelles giant tortoise, called Jonathan, is believed to have been born in 1832, making him 190 years old in 2022.

Tortoises’ extreme longevity has always fascinated us humans. And, according to a new study, we may have found the secret to their long lives. But another animal is starting to gain some traction for dipping into the waters of the Fountain of Youth: aging slows to a crawl when yellow-bellied marmots hibernate.

Tortoise cells: supersensitive to stress

A new study that was published on November 18, 2021, in the science journal Genome Biology and Evolution revealed that compared with other turtles, tortoises have evolved to have extra copies of genes (called “duplications”) that may protect against the ravages of aging, including cancer.

Laboratory tests on the cells of Galapagos giant tortoises show that the animals have developed such defenses. Specifically, researchers stressed the tortoises’ cells in ways that are associated with aging to see how well they resisted. When exposed to such pressures, the scientists found that these reptiles’ cells self-destruct much more readily than other turtle cells through a process called apoptosis. Destroying glitchy cells before they have the chance to form tumors could be helping the giant tortoises evade cancer.

These findings are particularly intriguing because you’d expect that huge animals that live for a long time should have the highest cancer rates. That’s because big, long-lived organisms have many more cells; and the more cells a body has, the more opportunities there are for cancerous mutations to arise.

Hopefully, in time, we’ll better understand the biological mechanisms that help large animals such as Galapagos tortoises to have such long lives. That research could have practical implications for humans, too. If we can identify the way in which nature has done something—for example, how certain species have evolved protections—maybe we can somehow translate those discoveries into things that will benefit human health, such as a drug that mimics how the tortoise cells function.

Research of this kind also underscores the value of conservation and why preserving biodiversity is so important. Many species probably hold a wide variety of secrets for dealing with major human challenges, such as aging, cancer and even climate change. This study shows that even within turtles, different species look, act and function differently. Losing any of them to extinction means that a piece of unique biology will be lost to the world forever.

Marmot DNA: modifications to metabolism

Another animal—yellow-bellied marmots—solves the aging riddle in another completely natural way: they hibernate from September to May every year.

Marmots are giant ground squirrels that can virtually halt the aging process during the seven to eight months that they spend hibernating in their underground burrows, according to a team of biologists at the University of California, Los Angeles (UCLA). Publishing their findings in the science journal Nature Ecology and Evolution in March 2022, the researchers state that theirs is the first study to analyze the rate of aging among marmots in the wild, showing that this antiaging phenomenon kicks in once the animals reach two years old.

Working in Colorado, the UCLA researchers studied 73 female yellow-bellied marmots, collecting and analyzing blood samples every two weeks over 14 active seasons. The marmots’ chronological age was calculated based on the date at which juveniles first emerged from their natal burrows. The scientists then built statistical models that allowed them to estimate what occurred during hibernation.

Hibernation is an evolutionary adaptation that allows animals to survive in harsh seasonal environments where there is little to no food and temperatures are very low. It’s common among smaller mammals, such as marmots, who are native to the mountainous regions of southwestern Canada and the western United States.

Marmots’ hibernation alternates between periods of metabolic suppression that last a week or two and shorter periods of increased metabolism, which generally last less than a day. During metabolic suppression, the marmots’ breathing slows, and their body temperatures drop dramatically, to the point that they feel like cold, fuzzy rocks. In addition, they use a miniscule amount of energy, burning about a single gram of fat a day—essentially nothing for a seven- to 15-pound animal. This allows them to save energy and survive long periods without food.

During their active summer season, however, marmots eat a lot, doubling their weight so that they have sufficient fat to survive the next hibernation period.

The UCLA researchers assessed the biological aging of the marmots based on what are known as “epigenetic changes,” hundreds of chemical modifications that occur to their DNA. They found that epigenetic aging essentially stalls during hibernation. Then, it increases during the active season, stops during hibernation and continues to increase in the next active season. This process helps explain why the average life span of a yellow-bellied marmot is longer than would be expected from the animal’s body weight.

These hibernation-related conditions—diminished food consumption, low body temperature and reduced metabolism—are known to counter the aging process and promote longevity, the researchers say. This delayed aging is likely to occur in other mammals that hibernate because the molecular and physiological changes are similar.

This study shows that there may be biomedical advantages to inducing hibernation conditions in humans or in human cells; for example, to preserve organs for transplantation or as part of long-term space missions.

Celebratory occasions: turtle days and marmot moments

Around the globe on World Turtle Day, people dress up as turtles, wear green clothes or participate in presentations about how we can help tortoises and turtles survive and thrive.

I also found out that there is an annual Marmot Day, too, which takes place on February 2 every year. It’s an Alaskan holiday that became official in 2009, when the 26th Alaska State Legislature officially passed Senate Bill 58. A luncheon is a traditional part of the celebration, and local newspapers report that “marmot jokes and gingersnaps are shared.” On that day, however, I don’t know if Alaskans dress up like marmots or not.

But whether or not once a year—let’s say, for a particular festival—you wear a cardboard shell on your back, dress in faux fur or simply show up in your own, human skin, I hope that one day in the near future you’ll take a moment to think of a tortoise or a marmot, and send them your thanks for helping you and, most likely, your descendants to live a very long life.

Here’s to finding your true places and natural habitats,

Candy