Can animals help people live longer?
If you’ve ever owned a pet, you understand how much it hurts to lose a beloved member of the family after 10 or 15 years. The lifespan of a pet is just a small fraction of a human’s. Now scientists are studying the lifespans of our dogs, cats, hamsters and horses to see how this knowledge can be applied to humans.
Lifespans of animals
Before we get into the why, let’s look at how long some of our furry and feathered friends live on average.
Drone Ant:3 days
Bees: 4 weeks
Hamsters: 2-5 years
Humans: 80 years
Whales: 40-200 years
Red Sea Urchin: 200 years
Jellyfish Turritopsis Dohrnii: Possibly immortal
Average lifespan is just an average, which means that it differs on an individual basis. For example, insects tend to not live long because they usually just have one mission- once achieved, they die. Not to mention billions of new insects are hatched every day. If they didn’t die quickly, the world would be overrun.
Dogs are a common house pet and the average lifespan is 10-14 years, but some breeds live for longer or shorter periods of time. Some dogs with compressed respiratory systems (like certain bulldogs) tend to live around 8 years, where smaller dogs can live for 20 or more years.
Humans have a broad lifespan as well. Because of medical advances, people who live to 100 are more common than ever before. Our average lifespan also factors in things we have data for, including accidents, illness, or other reasons people may die younger.
Whales have such a broad average for the simple fact that they’re a little more difficult to study since they live in the ocean and we don’t. In 2007, a bowhead whale was found with a harpoon tip lodged in its skin. The harpoon dated back to the 1800s, meaning that particular whale had been swimming around for at least 115 years.
Why do lifespans differ?
There are simple and more complex explanations for why animals live longer than others.
The simple and more obvious explanations are:
Animal size. Larger species tend to live longer. There are exceptions, but for the most part, bigger animals have longer lifespans.
Eating habits. Plant eating animals tend to live longer lives relative to size in comparison to those who eat meat.
The food chain. Big animals are less likely to get eaten by another animal, so they live longer.
Environment. Sadly, the world is changing because of the actions of humans. Polar ice caps are melting, so animals like penguins and polar bears are living shorter lives because they aren’t evolving quickly enough to keep up with the environmental changes. Deforestation affects the habitats and food supplies of many animals. Pollution has an effect as well as it can poison animals.
Mutation may be the key
Source: Nature 604, pages517–524 (2022)
As we age, we tend to be more prone to certain things like heart disease or cancer. Your cells replace themselves during your life, and mutations happen when they replicate. And as those cells divide, the mutation gets passed on to the next generation of cells. The assumption has always been that species with a slower mutation rate live longer. This is called the somatic mutation theory.
Researchers collected samples from 56 individuals from several species. They collected tissue from mice, rats, humans, monkeys, cats, cows, dogs, ferrets, giraffes, dolphins, horses, lions, naked mole rats, rabbits, lemurs, and tigers.
The samples they collected were of intestinal crypts, which are structures inside colon walls, consisting of cells that reproduce quickly. Because the cells from each individual were from the same tissue, this allowed a uniform study of mutation rates across all species.
The results from the study showed a correlation between lifespan and the rate of mutation. If the species tends to have a shorter lifespan, the mutation rate is faster. What is interesting is that no other factor, including weight, had any effect. In short, the slower the rate of somatic mutation, the longer the lifespan.
What does this mean for people?
The whole idea behind studying other species might reveal secrets to why some live longer and how it can be applied to help humans achieve longevity. We do know that somatic mutations don’t cause aging, but they do contribute to it. So if a cell mutates into a cancerous cell and the mutation rate is higher, it’s more likely that cancer will occur.
Humans and other animals have special genes that can help stop the growth of runaway mutated cells so that they don’t replicate to the point where they cause cancer or disease. But, sometimes these genes can be damaged when they replicate themselves. There are animals, such as the Bowhead whale and naked mole rat, that have multiple copies of these special protective genes- it’s sort of like a backup. If one copy is damaged, there is still backup protection to fight damaged cells.
Unfortunately, just increasing these special genes can have negative effects. In mice, adding just one extra gene to the line of defense made it harder for stem cells to reproduce, which caused other problems. It seems like the solution to using genetics to prolong life in humans will require finding the right combination. That isn’t an easy task.
The studies continue
The new study is just the tip of the iceberg and many more are coming. Now that scientists are learning more about somatic mutation theory and how it affects aging, they want to learn more. Additional studies will help them learn more about how it works in humans and are a potential key to developing ways to fight aging and age related diseases.