What is the limit of human lifespan?

How long can humans live? Could we ever see a day when it’s normal to live to 100, or 150, or even longer? In this post, we’ll look at the science of longevity and what the latest research says about the upper limit of our lifespans.

Do we live longer lives today than in the past?

A baby boy born in Sweden in the 1750s could expect to live to 33 years old. By the 1850s, life expectancy had increased to 40. And by the 1950s, the average boy would live to see 70. Today, Swedish baby boys have a life expectancy of 80 years.

Did we really add fifty years to our lifespans in just a couple of centuries? Yes and no. Life expectancy at a national or global level is the average of everyone who lives and dies, and that means those numbers can be deceptive. In 1800, a quarter of Swedish babies didn’t survive their first year. Today, 98% do.

Losing a quarter of your population every year before they turn one has a huge impact on life expectancy statistics. It dramatically reduced the average age of mortality, and makes it look at first glance like everybody in the past was dying incredibly young. However if people in the past survived childhood, they had a very good chance of reaching old age.

A Swedish man aged fifty in 1750 could expect to live another 18 years. A 65-year-old still had another decade on average. According to Psalm 90 in the Bible, “The days of our years are threescore years and ten.” That suggests the average person lived to about 70 years old, even 2000 years ago. That’s not much different to the average age people reach today.

What factors affect longevity?

The biggest factor that impacts our longevity — and is the reason for the dramatic rise in national and global life expectancy — is science. We know more than ever about how to identify and treat different diseases.

The first vaccine was developed in 1798, to prevent smallpox. The disease had killed around 400,000 people in the previous century. Today we have vaccines against all kinds of diseases that used to be killers, and smallpox has been completely eradicated — the first time humanity had ever made an infectious disease extinct.

Huge advances in medicine and science have had a major impact on longevity, helping us all to live longer, healthier lives. However even with these advances, the biggest change has been seen at the lowest end of our lifespans. Infant mortality rates have plummeted in the developed world, but a healthy adult living today has only gained about a decade of life expectancy on his five-times great-grandfather.

Another major factor affecting longevity is nutrition. The United Nations estimates that 25,000 people, including 10,000 children, die from hunger every day. Worldwide, more than 850 million people do not get enough to eat.

Poor nutrition, either in terms of lack of food, or lack of the right vitamins and minerals from food, has killed millions of people throughout history. Today, many people have access to a much broader diet and a variety of nutritional supplements. The improvement in our diets has also helped raise our lifespans, and explains why adults now usually live longer than they did in the past.

The rise of centenarians

While history is full of tales of people who lived to 100, 200 or even longer, very few early cases have been documented of true centenarians (people who lived to 100+). At the turn of the twentieth century, a Bulgarian census documented 1756 centenarians, but researchers could only verify 51. 

There are lots of reasons why people might lie about how old they really are, from wanting fame and notoriety, to claiming assistance in the name of a deceased parent. That’s part of the reason why scientists have been cautious about studying centenarians and supercentenarians. It’s super hard to verify if someone really was born 100+ years ago, because official records of their lives are often missing or incomplete.

There are around 451,000 documented centenarians alive today, or 0.006% of the global population. Some countries have more centenarians than others. For example globally there are 6.2 centenarians per 100,000 people. But in India, there are only 2.1 centenarians per 100,000. And in Japan, there are 68.5 per 100,000. Factors such as nutrition and medical access make it more likely that people in developed countries will reach 100 years old.

Centenarians are the fastest growing population demographic in the developed world. In 1999, 0.029% of adults were centenarians. By 2015, that had increased to 0.074%. By 2050, researchers estimate that figure will be 0.236%. That’s still not many people, about two in a thousand, but it’s a tenfold increase in just fifty years.

What is behind this dramatic rise in our longevity? If it took us over 200 years, from 1750 to 1950, to add an extra ten years to our lifespans, how are so many more people suddenly reaching 100 or older? What changed in the last fifty years?

Part of the rise is probably due simply to paperwork. We can better verify now if somebody is telling the truth when they claim to be 100 years old. We also have better global communication than ever before, so researchers can trace centenarians who live in remote locations who in the past may have been overlooked. However this doesn’t explain the significant increases in centenarian numbers documented in just the last decade. It also doesn’t explain why the centenarians themselves are living longer than at any point before.

All about supercentenarians

A Dutchman, Geert Adriaans Boomgaard, was the first verified supercentenarian. He was 110 years old at his death in 1899. A supercentenarian is anyone who has reached the age of 110, and only about one in a thousand centenarians reach that milestone. That means there are about 450 living supercentenarians right now, and as of 2015, about 1700 supercentenarians had been documented in total.

In the 1980s, another record was smashed — the first person to live to 115 years old. Today there are six people alive who have reached that age, and 57 people total have been documented to have celebrated their 115th birthday.

What is becoming clear is that not only are more people making it to 100 than ever before, but we’re also starting to live longer beyond that milestone.

Studying the limit of human life

In 2016 a geneticist, Jan Vijg, and researchers at the Albert Einstein College of Medicine in New York City, began to explore the possibility of finding the limit to human lifespan. By looking at data about the oldest people to have lived over the past fifty years, Vijg and his colleagues decided that humans couldn’t live beyond 125 years.

They reached that conclusion because there had been few gains in maximum lifespans beyond 115 years since the mid-1990s. The oldest verified person to have ever lived, Jeanne Calment, died in 1997 aged 122 years and 164 days. Although an increasing number of people are making it beyond 115, Calment is the only person to have ever verifiably passed 120.

The problem with Vijg’s conclusion is it only looks back, not forward. This model doesn’t account for the rising number of people becoming centenarians, or the small but steady increases in their overall age. No human has made 125 so far, but that doesn’t mean it isn’t possible.

A new study in 2018 took a different approach to longevity. Elisabetta Barbi, a demographer at Sapienza University, and statistician Francesco Lagona of Roma Tre University, looked at the statistical probability of death over time. They found that the “hazard rate” of dying plateaus after we reach 105 years old.

As we age, our chance of dying fluctuates. Infants often die of infections that most adults survive, so they have a lower survival rate. Then when we reach young adulthood, the chances of dying in the next year decrease. In old age, the odds of death start to climb again.

AGE	DEATH PROBABILITY (MALE)	DEATH PROBABILITY (FEMALE)
0	0.006081	0.005046
10	0.000097	0.000096
20	0.001079	0.000405
30	0.001798	0.000811
40	0.002581	0.001423
50	0.004888	0.002980
60	0.011447	0.006880
70	0.022364	0.014662
80	0.056205	0.041102
90	0.161582	0.128749
100	0.347900	0.299540

Source: SSA Actuarial Life Table

After 105, according to Barbi and Lagona, the chance of dying in the next year is about 50/50. That means that there is never a point at which our deaths become certain. Theoretically, we could live forever.

The problem with this is it’s all theoretical. The study doesn’t consider if our bodies are physically capable of keeping going for that long, or if there are mechanisms inside us that must eventually shut down and cause our deaths. The statistical analysis of longevity is interesting, but it overlooks biology. But the study did reopen the debate about whether or not there’s a hard limit on how long it’s possible for a human being to live.

Looking for proof of a limit to human lifespans

In 2021, a new study looked at the question of how our bodies age, and if we’re capable of living indefinitely. We already know that our cells can only replicate so many times. This is called the Hayflick Limit. Although the Limit is different for each of us, once we reach it, our cells begin to age and die.

Scientists are researching several ways of extending our Hayflick Limit and helping our cells to live for longer. One of the most important things we’ve learned about how our cells age is that there's a difference between our biological age — how much wear and tear our bodies have suffered — and our chronological age, or how many years we’ve been alive. Staying healthy at a cellular level is probably the key to extending our lifespans.

The study, published in the journal Nature Communications, looked at how long our cells could function under ideal circumstances. The researchers found that over time, our cells lost the ability to heal and regenerate. Even under the best conditions, this process couldn’t be stopped or reversed. They calculated that our bodies reach a “critical point” after 120-150 years, beyond which our cells are too broken to sustain life.

The researchers concluded that death was an “intrinsic biological property” of our bodies, and this breakdown was inevitable no matter what we did. That means it’s impossible for anybody to live beyond 150 years without huge scientific advances. We would have to develop therapies to reprogram how our cells work in order to live any longer.

The science of anti-aging

In recent years, scientists have learned lots about how our bodies age, but we’re still only at the beginning of understanding and controlling our longevity. The advances we’ve already made in healthcare and nutrition have made a big difference to human life expectancy. As we learn more about how our bodies age at a cellular level, it could soon become the norm for people to live to 100, 150, or even longer.