When I'm 164: How Can Bioscience Push the Limits of Lifespan?
We may be closer than most realize to significant increases in life expectancy.
(garryknight/Flickr)
In 1835, Charles Darwin reached the Galapagos Islands aboard the HMS Beagle. While there, someone (possibly Darwin) captured a tortoise named Harriet. She lived for 176 years, finally dying in 2006.
Other organisms in nature are known to live considerably longer than Harriet. These include the Methuselah tree, a bristlecone pine in Southern California that, at 4,843 years old, is perhaps the oldest known complex organism on Earth. Other creatures that age very slowly and live up to hundreds of years, showing little signs of senescence (aging), include rockfish, clams, lobsters and jellyfish.
Humans, too, live a long time compared to most species. The longest-living primates other than humans are our closest relatives in evolution, chimpanzees. They have an average life span of 53 years. This makes the current life expectancy in the West of nearly 80 years, with a maximum life span of 120 or so. Quite long, though not in the same league as Harriet the tortoise or bristlecone pine trees.
As scientists make new breakthroughs in understanding the mechanics of aging, the upper limits of aging might be changing for Homo sapiens. Already, life expectancy has increased dramatically since the late nineteenth century, when it was 40 for males and 42 for females at birth, and age 58 and 59 respectively if they survived to age 10 (infant mortality was much higher in 1890).
Life expectancy is expected to keep rising to perhaps age 100 sometime in the 22nd century, according to the United Nations. This comes from better hygiene and nutrition, and also from bio-med breakthroughs that range from antibiotics to targeted therapies for cancer and robotic surgery.
Is it possible that new waves of discoveries might take us on a path of even more dramatic increases in life extension?
Until recently, mainstream scientists would have answered with an emphatic no, suggesting that this was a fantasy offered up by alchemists, charlatans, and pseudo-scientists. Two trends have shifted this point of view.
The first is a realization that aging is one of the greatest risk factors for many diseases, and therefore needs to be seriously addressed by biomedical researchers. Not with a primary endpoint of radically prolonging life, which remains controversial, but as a major element of conventional research into understanding and combating cancer, diabetes, heart disease, and other chronic diseases of the elderly.
The second trend is that scientists have succeeded in upping the lifespan of many animals, sometimes dramatically, discoveries that have launched wide-ranging research into the mechanics of aging. The big question is: Can these processes be replicated in humans?
Since becoming more legitimate in the 1990s and early 2000s, the field of longevity and anti-aging research has generated serious efforts to answer this question. Work is being conducted primarily in four different areas: Healthy Living and Predictive and Preventive Medicine; Genetics; Regeneration; and Machine Solutions. (I touched on some of this material in a recent New York Times article; here I will expand on what is happening in the field of anti-aging science.)
Healthy living and preventive medicine
Healthier living already has increased lifespans and prevented death for literally billions of people over the past 150 years. But we could still do more, especially to combat lifestyle conditions and diseases like obesity and diabetes, which prematurely kill millions of people a year. Billions also still live in poverty, with over one billion people facing hunger each day.
The science of predictive and preventive medicine is moving in fast to collect health data on people -- everything from one's DNA to measurements of environmental toxins and a host of other tests -- that might help predict their health future. Though much needs to be done to better collect and interpret this data, the field promises to be able to identify future risk factors for diseases such as cancer or heart disease before it happens.
Hopefully, this would give a person enough warning to take action to prevent or mitigate whatever malady might be coming -- though much needs to be done to understand the data being generated by, say, people who have had their DNA sequenced to see what secrets this might reveal.
One potential setback to the "healthy living" approach came this week in a new study in Nature. For 25 years researchers at the National Institute on Aging have been feeding rhesus monkeys a diet that reduced calories by 30% to see if primates react to a "caloric restriction" regimen by living longer and healthier. Other animals, including worms, flies and mice have reacted to eating less by living more years.
Surprisingly to many, the NIA study showed no lifespan increase, contradicting a study published in 2009 that showed a positive impact in the lifespan of monkeys fed a caloric restriction diet. Clearly, more work is needed to understand the impact of calories on longevity.
Nor is healthy living and prevention alone going to push lifespan to anyone to age 150. For that, a more engineered boost will be required.
Genetics
For 30 years mainstream scientists have been trying to better understand the process of aging at the genetic and cellular level, as well as in entire organisms. They have succeeded in manipulating genes and proteins that seem to regulate lifespan in worms, flies, mice and other critters -- sometime upping lifespan by many times. Perhaps more importantly they slow the aging process by delaying or preventing diseases of aging like heart disease and diabetes. A number of pharmaceutical companies are developing pills for diseases of aging like diabetes and inflammation, testing chemicals that activate enzymes linked to increased lifespans in mice and other animals. They may work in bumping up lifespans for humans, too, though no one yet knows for sure.
Regeneration
Scientists have succeeded in using stem cells - the special cells that replace dying cells in different organs -- to regrow or repair hearts, livers and other tissue in animals. They have had some success in regenerating tissue in humans, but only for simple organs like a bladder or bone marrow. Using stem cells to regrow, say, cells in the heart or brain remain many years in the future.
Machine solutions
People have long fused machines and engineered devices and tools to human biology to improve or treat conditions, injuries and disease. These include everything from eyeglasses to pacemakers and joint replacements. More recently inventions and breakthroughs are linking devices to the brain to help patients with Parkinson's disease control tremors and to help some people who are deaf to hear again. Other experimental machine-brain interfaces may soon allow the paralyzed to operate computers using thought.
Whether science really will boost lifespan dramatically in the near future is still open to question. Some anti-aging enthusiasts believe that substantial leaps could occur within a few years; most believe it will be a matter of decades, though few doubt it will happen.
This brings up the question: what happens if radical life extension actually works? How will it impact individuals, society, and even the planet? I'll address these queries in a subsequent piece for The Atlantic next week.
This post is part of an Atlantic series adapted from the ebook When I'm 164: The Science of Radical Life Extension, and What Happens If It Succeeds.