Can we reverse aging? These scientists are rethinking the limits of human lifespans
We tend to think of getting older as inevitable, but what if it’s actually something we can control? Researchers like David Sinclair and Nir Barzilai have discovered some of the secrets to reversing aging, found animals who defy our understandings of life, and turned old mice young again. But even if humans could live forever, should we?
In the past century alone, humans have more than doubled their lifespans — a pretty remarkable accomplishment! But such a drastic change has raised a lot of questions for our species to consider.
What do longer-living humans mean for our world? And who’s to say that our lifespan couldn’t triple or quadruple in the next century — will humans be living until 300 some day? And is that something that we would actually want to do?
This may all sound like science fiction, but real-life scientists are already looking into these questions. On the debut episode of the KCUR Studios podcast Seeking A Scientist, host Dr. Kate Biberdorf (aka Kate The Chemist) explores the possibilities with some of the top researchers in the longevity field.
With our sudden (relative to the length of human evolution) increase in lifespan, humans have also seen a drastic increase in age-related diseases — namely diabetes, cancer, heart disease and Alzheimer’s.
“We know something very important about these diseases. What drives them is this aging,” says Dr. Nir Barzilai, director of the Institute for Aging Research at the Albert Einstein College of Medicine.
“So we’re saying, let’s intervene in the biology of aging and prevent all those diseases.”
Barzilai is one of the leaders in the growing scientific field commonly referred to as “aging science” or “longevity research.” Another big name in the field is Harvard's genetics professor David Sinclair — you might know him from a famous 2018 experiment where he essentially turned back the biological clock of a mouse.
Don’t confuse this research with the pseudoscience of “anti-aging,” things like Botox treatments and dietary supplements.
Scientists like Sinclair and Barzilai, instead, are looking at aging from a biological perspective.
In his research, Sinclair crushed the optic nerve of a geriatric mouse, injected it with a special cocktail of genes, and monitored it for any signs of growth. In three weeks, the old nerve started to grow back to the brain, restoring the mouse’s sight -- a feat thought only to be possible for new, youthful nerves.
That experiment, and other work in Sinclair’s lab, has left him with new revelations about the meaning of age. “I also realized that aging was going to be truly reversible,” Sinclair says.
We aren’t meant to live forever, but it’s in our nature to try pushing the limits of those boundaries. Here are some answers to the big questions about aging and what we can do to stop it.
What even is aging?
According to the National Library of Medicine, aging is defined as “the time-related deterioration of the physiological functions necessary for survival and fertility.”
Scientists can track these changes by watching for mutations in our DNA, such as the attachment of methyl groups (a cohort of atoms that include one carbon and three hydrogens). The more methyl groups you have, the “older” your body is.
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Why do some species live longer than others?
Our chronological age does not match our biological age. Basically, the number of times our body has orbited around the sun has nothing to do with what’s going on inside our bodies. Throughout our entire lifetime, cells are continuously regenerating and dying.
“Every organism has their own clock of how long they’re going to be alive,” says molecular biologist Alejandro Sánchez Alvarado, executive director at the Stowers Institute for Medical Research. (Disclosure: the Stowers Institute financially supports KCUR’s podcast Seeking A Scientist.)
Sánchez Alvarado spends a lot of time in the lab looking and thinking about how species like flatworms, salamanders and even plants age. He’s one of the many scientists exploring how plants like the Azorella Compacta live to be 3,000 years old. These plants — which look like big, green, plush fur balls — grow as slow as 1/18th of an inch every year.
You’ve probably heard the phrase “dog years.” It’s not entirely accurate, but scientists have learned that dogs go through the same biological changes in eight weeks that humans do in nine months.
As far as we know, all biological systems naturally go through a process called tissue homeostasis, which fixes the normal wear-and-tear of our organs -- humans appear to just be better at it than dogs. Whales, who can live to be over 200 years, are even better than humans.
Meanwhile, the jellyfish Turritopsis dohrnii has been described as biologically immortal.
What’s the average human lifespan?
Dr. Nir Barzilai says throughout human evolution, our life expectancy has grown. There have always been “older” people, or outliers, who live longer, but the typical life expectancy stayed consistent at around 20-30 years old, due to high infant mortality rates.
“Most people didn’t die from Alzheimer’s or diabetes or cancers,” Barzilai says. “They never got to be this age.”
However, in the past 150 years, our life expectancy has jumped — mostly because of advancements in agriculture and technology, and innovations in sanitation like clean water, sewers, and vaccinations.
By the middle of the 20th century, people who survived childhood lived to be an average of 50-55 years old.
Now, the average human lifespan is now 80 years old in most of the world.
But the average lifespan is 76 (and falling) in the United States. Americans are particularly susceptible to homicides, opioid overdoses, obesity, suicide, smoking, and road accidents, at a higher rate than other first world countries.
Even within a country like the United States, there are also environmental discrepancies to consider — like access to health care, and resources. For example, people working multiple jobs or living in rural areas far from a hospital may not have the time or opportunity to seek proactive screenings or treatments, such as pap smears or mammograms.
According to Barzilai, in the United States people living in poverty live 20-30 years less than rich people.
So why can some people live to be over 100?
The oldest verified human was Jeanne Calment, a French woman born in 1875, who lived to be 122 years and 164 days old. Before she died in August 1997, she met Vincent Van Gogh (she described him as kind of rude,) saw the Eiffel Tower being built, and experienced technological advancements from the light bulb to the computer.
Calment was a wife and mother, enjoyed roller skating and rode a bicycle until she was 100. And she became a pretty big celebrity due to her age — although some claimed she was a fraud.
But her age was eventually verified and then, of course, heavily researched. She was even featured in a techno dance album!
Barzilai wants to understand from a genetic standpoint why some people like Calment live to be 100 (or beyond,) and others do not. Under the Longevity Genes Project, he’s been working with a group of centenarians (people who live to be at least 100 years old) and their families.
What he’s found is that centenarians contain a special set of longevity genes, which protect themselves from other genetic mutations known to be otherwise fatal.
What can I do to live a longer, healthier life?
Everybody wants the quick answer and the secret to slowing down aging. But the truth is a combination of genetic and environmental factors.
In Barzilai’s book, “Age Later: Health Span, Life Span and the New Science of Longevity.” he lists four things that are proven to help:
- Maintaining healthy eating practices
- Regular exercise
- Sleep (the more the better)
- Social activity
Sinclair agrees, especially the last point.
“If you’re lonely at home, get a pet,” he says. “Get some friends, it’s really important. And not friends that stress you out. Friends that you can really call and cry on the shoulder of, those are the important ones. They’re really rare. If you’ve got a friend like that, really work hard to keep them and be a good friend to them as well.”
Sinclair also recommends eating more colorful plants (he has gone vegan), cutting your alcohol consumption, and eating less sugar. And don’t be afraid to go outside and take a walk, even in the cold -- believe it or not, Sinclair says cold air keeps that biological age down.
What’s next in aging research?
Sinclair likes to say that the first person to reach 150 years old has likely already been born.
He likens aging research now to where cancer research was back in the 1960s, with a lot of promising results coming in the near future.
Sinclair dedicates his book, “Lifespan: Why We Age And Why We Don’t Have To,” to his great-great-grandchildren, who he believes he will meet one day.
“We’ve discovered that there’s backup software that can be rebooted in our bodies in every cell and it’s safe,” Sinclair says. “And you might say, well that’s for our grandkids to reap the benefits of, and I don’t think so.”
Just recently, Sinclair turned geriatric mice into what he refers to as "marathon runners" by giving them an aging booster shot. He also used human tissue to grow tiny human brains, called organoids, to study dementia. More importantly, Sinclair has introduced mutations to the brain known to accelerate Alzheimer's, allowing his lab to study the changes associated with aging.
“Often people say, ‘Why would I want to live any longer if I’m just going to get dementia?’ So it’s really important that any technology we come up with that slows down and reverses aging, includes the brain,” Sinclair says. “After we’ve rejuvenated the eye and cured blindness, the next goal would be to try to cure hearing, and then the entire brain, treat Alzheimer’s disease.”
He says humans have engineered everything else in our world, and aging is next. “There is no law of biology that says we have to age at 50 and start to decline,” he says. “One day we are going to be able to choose when we die.”
Where can I hear even more about this topic?
Listen and subscribe to the first episode of Seeking A Scientist with Kate The Chemist, from KCUR Studios, available wherever you listen to podcasts.
Seeking A Scientist is a production of KCUR Studios, made possible with support from the Stowers Institute for Medical Research and design help from PRX.
This episode was produced by Dr. Kate Biberdorf, Suzanne Hogan and Byron Love, edited by Mackenzie Martin and Gabe Rosenberg, with help from Genevieve Des Marteau.
Our original theme music is by The Coma Calling. Additional music from Blue Dot Sessions and Jeanne Calment, the oldest verified human.