How Long Could Humans Live For?

Emma Hazelwood

Humans have fixated on the concept of death for thousands of years. But what if there was no death; no limit to human lifespan?

Image Credit: Free Stock Photos

The oldest human on record is 122-year-old Frenchwoman Jeanne Louise Calment. She was born a year after Alexander Graham-Bell invented the telephone, and died the same year scientists first successfully cloned a mammal – outliving her husband, daughter, and grandson.

Although life expectancy has increased during the 20th century (in developing countries it has almost doubled in 100 years), many scientists claim that human lifespan has hit its limit.

Studies on countries with a high proportion of those aged 110 and above, show that the maximum age at death increased between 1970 and the early 1990s but then plateaued when it reached 115 years old. Those aged 70 and up have seen vast rates of improvement, both in survival and quality of life. However, for those aged 100, these factors have remained mostly unchanged.

One reason for this proposed by Henne Holstege from VU university is that if you die from heart disease at age 70, the rest of your body might still work; if doctors can save your heart, you may survive. However, for those aged 100 years old, all bodily systems are frail – if you get heart disease, doctors may save your heart, but instead you are likely to die from something else.

There are scientists who disagree with this, and claim that there is no ceiling to human lifespan. Based on a mathematical assumption, some claim that the first human to live to 1000 years old is already alive. If you are 25, you have a 0.1% chance of dying before your 26th birthday. If we can maintain this likelihood of death throughout human lives, statistically, you will live to be 1000 years old.

There are a few examples in the animal kingdom of apparent immortality and reverse ageing. Tardigrades, for instance, also known as ‘water-bears’, are micro-animals capable surviving in a dry state for 30 years, then ‘coming back to life’ when rehydrated. Turritopsis dohrnii, known as the ‘immortal jellyfish’ is capable of actually reverse ageing back to its larval form.

Most of the research into extending human life is not just aimed at enabling people to live longer, but at increasing human ‘healthspan’ – the years in which you are free of frailty or disease. Instead of attempting to cure specific diseases, which is the usual route for biomedical research, this area focuses on slowing down the entire ageing process.

Scientists have already successfully slowed ageing in a variety of animals.  Many claim that there is no reason to believe this couldn’t be achieved in humans. Over 20 drugs have been found to slow down the ageing process. Some of these are already being used, such as metformin, which treats diabetes.

Rapamycin aids organ transplants and treats rare cancers, but has been shown to extend life expectancy of mice by 25% (the longest achieved so far by a drug), and protects them against diseases associated with ageing – such as cancer and neurodegeneration. When tried in a human trial on healthy elderly volunteers, rapamycin appeared to reduce susceptibility to flu (associated with old age) by 20%. However, no drug has yet been found which slows down all signs of ageing.

Things which were once thought impossible – vaccines, flying, IVF – are now accepted as a part of everyday life.  Cynthia Kenyon, of Calico (California Life Company) points out that no one would have predicted that altering a single gene could slow the ageing process and double the lifespan of animals, but it can. We know that the process of ageing is, at least to an extent, malleable, so why shouldn’t we believe we can extend human life beyond current barriers?

This brings us to the issue of, not whether we can extend human lifespan, but whether we should. Already, research into increasing human life expectancy has caught the eye of rich businessmen. A researcher who showed that blood plasma from young mice restored mental capabilities of old mice claims to have been approached by many ‘very rich people’, asking him if he could help them live longer. Some believe that anti-ageing medicine will be the biggest industry to ever exist. Resveratrol was bought by GlaxoSmithKline for $720 million after it was shown to extend the life of yeast cells and produce favourable effects in mice.

Could the success in extending human lifespan lead to a society where the rich live forever and the poor die young?

This is not to mention the other economic impacts of an older population. Young people may struggle to get a job if the market is dominated by a healthy elderly generation with years of experience. Also, the government may spend less on the NHS, but more on pensions and state benefits.

As human life expectancy has shot up over the past few decades, age-related diseases such as Alzheimer’s are at an all-time high. As we go on preserving life at all costs, are we extending not the time spent truly living, but the time spent suffering? Until science can offer not just a longer life, but a longer healthy, happy life, should increasing human life expectancy be pursued?

Some psychologists worry that, as people live longer, they will feel less of a need to make each day count. As author Rick Riordan wrote, “Life is only precious because it ends.”

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