The genetic secrets that help some animals defy aging (Part 3 of 3)

By Leslie Alan Horvitz

Rougheye rockfish

These deepwater fish are found in the North Pacific. They can live for over 200 years. Many other rockfish can only live up to 11 years. Rougheye rockfish, however, generally start breeding at age 25, and they produce more and stronger young as they get older. Because rockfish comprise more than 100 species, with lifespans ranging from 11 to over 200 years, researchers have utilized them to study the phenomenon of longevity. They have found that genes that normally regulate steroid hormones, which affect how long an organism takes to reach sexual maturity, may explain why this particular species has a longer lifespan than its relatives.

The flavonoid metabolic pathway (controlled by these genes) may be among the biological pathways that influence longevity, and this applies not only to rougheye rockfish but also to humans. “Nature presented us with an experimental design in the form of rockfish, and we wanted to see if we could pull data from it,” says Matthew Harris, associate professor of genetics at Harvard Medical School. “It’s incredibly impressive and valuable that this actually worked. It shows how comparative genomics can detect signals from millions of years of evolution to help us understand the networks of genes that interact to regulate complex phenomena such as longevity.”

Koi

These large goldfish, native to Japan and prized especially for their beauty, typically live 15 to 30 years, although some have been known to live up to 200 years. However, they are indulged by humans, which explains why they can live so long. Even in captivity, other fish seldom live 40 years or longer. The koi that reach the century mark and beyond may also owe their longevity to breeding, as Japanese breeders take great care to maintain the gene pool of these fish, keeping the most valuable and longest-lived in Japan and exporting others that don’t meet their exalted standards.

Greenland shark

Also known as the gurry or grey shark, this fish is typically found in the waters of the North Atlantic and Arctic. But because these sharks live at great depths (an average of 2,568 feet), they haven’t been well studied. What is known about them is that they can live to very advanced ages—250 to 500 years, the longest known lifespan among vertebrates. They’re extremely big (they measure between 8 and 23 feet and weigh 3,000 pounds or more) and reach sexual maturity only at 150 years.

Their pups are born alive after a protracted gestation period that ranges from 8 to 18 years. Researchers believe that their slow metabolism is a key factor in their long lifespan. These sharks move through the depths at speeds of less than 10,000 feet per hour (about 1.8 miles per hour). Compare that rate to that of the great white sharks, which can travel up to 35 miles an hour. On the other hand, no other sharks can withstand the extreme Arctic cold year-round. Greenland sharks may also benefit from the protection afforded by the methylated compounds in their muscles. These compounds play a role in gene regulation.

Jellyfish

A standout among jellyfish, Turritopsis dohrnii possesses a unique trait that makes it immortal—or as close to immortal as a living organism can be. This species has the ability to revert to its juvenile polyp stage after reaching sexual maturity. These jellyfish begin their lives as free-swimming larvae that eventually develop into colonies (collections of cloned polyps). In the event of environmental stress, a threat to its well-being, sickness, or age, the jellyfish can revert to its original polyp state and form or join another colony.

Turriopsis dohrnii can pull off this trick through a process called transdifferentiation, which transforms old cells into new cell types. In theory, this process can go on indefinitely. Immortality, though, is seldom reached because of predation or disease in the earliest medusa stage, cutting these creatures off before they can revert. Nonetheless, their capacity to revert—and, in theory, live indefinitely—has attracted the interest of researchers studying aging, which may ultimately lead to the development of regenerative therapies or age-delaying drugs in humans.

The Resurrected Worm

A humble worm may have won the long-life competition. The discovery of an apparently long-dead worm in the Siberian permafrost in 2023 has prompted scientists to reassess the longevity of an organism. After being frozen for approximately 46,000 years in the permafrost, the worm Panagrolaimus kolymaensis—a previously unreported nematode species in the scientific literature—survived and remained alive. It just took a bit of thawing. The worm appears to have benefited from a process known as cryptobiosis, which slows an organism’s metabolism. In this biological strategy, life seems to stop under icy conditions. This process has been observed in other creatures, such as tardigrades and particular species of brine shrimp. Because no significant metabolic activity occurs in a frozen state, animals can survive even lethal conditions until they are restored to an environment in which they can resume growth and reproduction.

The worm extracted from the permafrost appears to have spent most of its life in a state of suspended animation. Scientists believe that these long-lived creatures possess special molecules that stabilize cells, keeping them intact even under extreme dryness or temperature fluctuations. Similar molecules have been found in other organisms that are known to survive dehydration and freezing. A 2023 study of tardigrades, also known as water bears, by the National Aeronautics and Space Administration highlighted their ability to withstand harsh conditions in space. This suggests that these tiny beings may have developed defense systems against extreme radiation and severe temperature fluctuations.

“No one had thought that this process could last millennia, 40,000 years, or even longer. It is simply amazing that life can begin again after so long, in the state between life and death,” said Dr. Phillip Schiffer, a group leader in the Institute of Zoology at the University of Cologne.

Scientists hope that, if they can isolate the genes in these nematodes that protect cells against freezing and radiation, they can store human tissue in cold storage and minimize damage from severe cold or dehydration. Although the worm unearthed from the permafrost has died, this type of worm generally lives for only one or two months. Its offspring remain alive in controlled conditions.

Oaks

The oldest individual oak tree in the United States is the Pechanga Great Oak Tree in Temecula, California, estimated to be around 2,000 years old. The Jurupa Oak in Riverside, California, which is estimated to be 13,000 years old, isn’t one tree; it’s a colony of trees with the same DNA; that is, it has cloned itself. The cloned trees form only after wildfires, when the burned branches of the original trees sprout new shoots.

Baobabs

Found in the savannas of 32 African countries and playing a role in many remedies, the baobab is one of the world’s oldest trees. It predates both human beings and the splitting of continents 200 million years ago. The tree is a succulent, absorbing water during the rainy season and storing it in its wide, cylindrical trunk during the dry season. It produces a nutrient-dense fruit that earns it its nickname, the Tree of Life. An iconic tree with an average height of nearly 100 feet and a crown of distinctively gnarled branches, it can live up to 5,000 years. “Baobabs are particular trees, with unique architectures, remarkable regeneration properties and high cultural and historic value,” says Adrian Patrut, a chemist at Babes-Bolyai University in Romania, noting that “they play an important role in carbon sequestration and create a distinct microenvironment.”

Bristlecone pine

The longest-lived tree is thought to be over 4,789 years old; it is a Great Basin bristlecone pine named Methuselah, located high in the White Mountains of California. Although other trees in the White Mountains and Aspen are older, they are clones of the same species, not individual trees like the bristlecone pine. This tree’s survival is due to its ability to thrive in environments where most other plants can’t. It can spread its roots far and wide in search of nutrients. Apparently, it is also relatively impervious to intense stress. This tree grows slowly because of the freezing temperatures, dry soil, and high winds in the area. Yet it can grow in both good and bad weather. Because it has a tough exterior, it is resistant to insect and pest infestations. Even as it ages and most of its bark dies, enough of the bark remains that the tree never dies entirely.

Redwoods

Individual redwoods can live up to a thousand years, but the species is believed to have lived on the planet for millions of years. There are three types of redwoods—coastal redwoods, giant sequoias, and dawn redwoods—and most are found in California. Some giant sequoias are estimated to be 3,000 years old. Coastal redwoods—some rising as high as skyscrapers 30 stories tall—are the tallest trees known. Because of their thick bark (up to 12 inches), the redwoods can withstand forest fires. Their canopies are vital to their health; by capturing water (often in the form of fog droplets), they effectively create their own rain.

Yews

Yews are among the longest-living trees in the world, capable of surviving for millennia. Some species, like the Pacific yew (Taxus brevifolia) of the Pacific Northwest, live for over 2,000 years, slowly growing into dense, evergreen forms. In Europe, yews have inspired awe for centuries because of their extraordinary age. The Llangernyw Yew in Wales is estimated to be between 4,000 and 5,000 years old, making it one of the oldest living organisms on the planet. Their ability to endure through centuries of environmental change, human activity, and disease highlights yews as a remarkable example of nature’s resilience and longevity.

The world’s oldest tree (possibly)

The Alerce Milenario, also known as Gran Abuelo (Great Grandfather), in Chile, is believed to have begun growing in 1630 BC and may be the world’s oldest tree. Only 28 percent of the tree is alive, primarily in its roots. Its surface is mainly covered with lichens and mosses. Scientists used a bore to penetrate the tree without harming it and found that it had 5,000 rings, which they used to determine its age, concluding that it was 100 years older than any of its rivals.

The Secret to Longevity Remains a Mystery

“The genetics of longevity are notoriously confusing,” says Dr. Mary Armanios, an oncologist and geneticist at Johns Hopkins School of Medicine. Confusing is right. Inflammation, which is associated with diseases of aging, is one factor. So is genetics. “Please study me,” pleaded Maria Branyas Morera, a Spanish citizen who, up until her death in 2024 at the age of 117, was the world’s oldest living person. Scientists have obliged, examining her blood, saliva, urine, and stool. They determined that her cells “seemed younger than her age.”

She lived a healthy life, walking a mile a day until she was over 100, and abstaining from drinking and smoking. And she consumed three yogurts a day. However, a healthy lifestyle wasn’t the only factor that contributed to her longevity. She was also found to have genetic variants reported to protect against common risk factors such as high cholesterol levels, dementia, heart disease, and cancer. In addition, she had a microbiome with an abundance of a type of beneficial bacteria, to which those yogurts might have contributed.

But nearly everyone who lives to a ripe old age—there’s a growing number of supercentenarians (those who live to 110 or more)—has a different explanation as to why they lived as long as they have while retaining all their marbles. The truth is that no one knows the secret to longevity, whether in humans, Greenland sharks, Galápagos tortoises, or bristlecone pines. Good genes are helpful. A healthy lifestyle, curiosity, and strong social relationships also play a significant role in contributing to why some individuals live to a great age. And yogurt can’t hurt, either.

(Leslie Alan Horvitz is an author and journalist specializing in science and is a contributor to the Observatory. His nonfiction books include Eureka: Scientific Breakthroughs That Changed the World, Understanding Depression with Dr. Raymond DePaulo of Johns Hopkins University, and The Essential Book of Weather Lore. His articles have been published by Travel and Leisure, Scholastic, Washington Times, and Insight on the News, among others. Leslie has served on the board of Art Omi and is a member of PEN America. He is based in New York City. Find him online at lesliehorvitz.com. This article was produced for the Observatory by the Independent Media Institute.)