The Lifespans of Our Ancestors || The Past That Shaped Us

THE LIFESPANS OF OUR ANSESTORS | The Past That Shaped Us

 Why the short lifespans of the past don't mean quite what they seem to mean

We often hear that people in ancient or medieval times lived only 25 or 30 years. It is an easy number to misunderstand. It can leave us imagining that a 30-year-old Roman or medieval farmer was already approaching the end of a normal life.

That isn't what the number means. Human beings have been capable of living into their 60s, 70s, and occasionally beyond for a very long time. What was dramatically different in the past was how many people survived long enough to reach those ages.

Understanding that difference changes the story of human longevity.

What Does a Life Expectancy of 30 Really Mean? Life expectancy at birth is an average. It estimates how long a newborn could expect to live under the mortality conditions of that particular population and time. For most of human history, one factor had an enormous effect on that average: many babies and young children died.

Imagine a community in which several children die before reaching age five, while many of those who survive childhood eventually live to 50, 60, or even 70. Average all of those lifespans together and the result can still be surprisingly low. That is essentially what happened throughout much of human history.

Disease, infection, poor sanitation, food shortages, accidents and complications of childbirth all contributed to early death. Without vaccines, antibiotics and modern medical care, illnesses that are routinely treated today could be fatal. The result was a world in which death was particularly common during the first years of life. So when we encounter an estimated historical life expectancy of 25 or 30 years, we should not picture a society in which most adults died at 30. We should picture a society in which many people never became adults at all.

People Still Grew Old

Older people were hardly unknown in the ancient world. Historical records, inscriptions, burial evidence and written accounts make it clear that some people lived into their 60s, 70s and beyond. The important difference was probability.

A child born today in a prosperous modern society has an excellent chance of surviving childhood. For most of history, that could not be taken for granted. Someone who successfully passed through infancy and childhood had already survived one of life's most dangerous periods.This creates an important distinction between two questions.

 One asks how long human beings were capable of living. The other asks how long the average newborn could expect to live. Those are very different things. The biological possibility of old age is ancient. The widespread expectation of reaching old age is comparatively new.

For Thousands of Years, Little Changed

Exact worldwide figures become increasingly uncertain the farther back we go. There were no national statistical agencies recording every birth and death in ancient Egypt, Rome, medieval Europe, or prehistoric communities. Nevertheless, demographic research suggests that life expectancy at birth remained remarkably low for most of human existence, commonly somewhere in the broad range of roughly 20 to 35 years.

Even as civilizations rose and fell, cities expanded, trade crossed continents and knowledge accumulated, mortality remained stubbornly high.Around 1800, estimated global life expectancy at birth was still only about 29 years.
Then the pattern began to change. The improvement was slow at first and unevenly distributed. By 1900, global life expectancy was still only about 32 years. But during the twentieth century the numbers began rising at a pace humanity had never previously experienced.

By 1950, worldwide life expectancy had reached roughly 46 years. By 1970 it was about 56 years, and around 2000 it had reached approximately 67 years. Today the global figure is above 70 years. In little more than two centuries, humanity had accomplished something that thousands of years of earlier civilization had not. - What Made the Difference?

There was no single discovery that suddenly extended human life. Instead, many improvements accumulated and reinforced one another. Clean drinking water and sewer systems reduced exposure to infectious disease. Better nutrition strengthened people's ability to survive illness. Vaccination prevented diseases that had once killed enormous numbers of children and adults. Antibiotics eventually turned many bacterial infections from potential death sentences into treatable conditions.

Childbirth became safer. Food supplies became more reliable in many parts of the world. Public-health authorities learned how diseases spread and how outbreaks could be contained. Medical knowledge, hospitals and emergency care steadily improved.
Some of the greatest gains came not from treating people after they became sick but from preventing them from becoming sick in the first place. And underlying much of the dramatic rise in average life expectancy was a profound change: more children survived.

When infant and childhood deaths declined, life expectancy at birth rose sharply. Later advances increasingly helped people survive the diseases and conditions of middle and old age as well.

From Surviving Childhood to Expecting Old Age

This helps explain why comparing a life expectancy of 30 in the distant past with one above 70 today can be misleading.The difference is not simply that modern people receive an additional 40 years of biological life. The earlier average included enormous numbers of lives cut short almost as soon as they began. Those who survived the dangerous early years often lived for decades afterward.

Modern societies changed that equation.

Infancy became much safer. Childhood became much safer. Pregnancy and childbirth became safer. Infections became more survivable. Then improvements in medicine began extending life at older ages as well. Gradually, something historically remarkable happened. Growing old stopped being an experience reserved for a relatively fortunate portion of the population and became an ordinary expectation for millions—and eventually billions—of people.

Lasting Impact

Longer lives have transformed society in ways that reach far beyond medicine. Families can now routinely include three, four, and sometimes five living generations. Grandparents may participate in their grandchildren's lives for decades. Education can extend further into adulthood. Careers may span 40 or 50 years, followed by retirement periods that themselves can last decades.

The change has also created new challenges. Societies must provide pensions, healthcare and social support for large older populations—circumstances that would have been unimaginable when relatively few people survived into advanced age. Perhaps most importantly, longer lives have changed our expectations. We make plans for decades ahead because most of us expect those decades to exist. That expectation is historically extraordinary.

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