Human Life Expectancy

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Podcast Transcript

Everyone, I have some good news and some bad news. 

The bad news is that you, me, and everyone else listening to my voice right now are mortal. 

As of the recording of this episode, time is undefeated. 

The good news is that there has never been a better time to be alive and that, historically speaking, life expectancies are at an all-time high. 

Learn more about life expectancies throughout human history and the things that improved them on this episode of Everything Everywhere Daily.

Before I begin, I should note the subtle yet important difference between the concepts of lifespan and life expectancy. 

The two are similar concepts but are different. 

Life span refers to how long the oldest members of a species can live. The maximum human life span appears to be around 115 to 120 years, depending on if you think Jeane Calment actually lived to 122, a subject that I covered in a previous episode.

Life expectancy is the average length of life for members of a species. It is literally just the mean value for everyone in a population.

Life expectancy, because it is an average, will always be lower than a theoretical life span. 

So, the discussion of human life expectancy began thousands of years ago in the Paleolithic period. 

Genetically, someone who might have lived 20,000 or 30,000 years ago wasn’t that different than you or me. However, their lives were totally different. 

In the words of the philosopher Thomas Hobbes, life was “poor, nasty, brutish, and short.”

Most of what we know from this period had to be cobbled together by archeologists and from old human remains. 

From what we can tell, the average life expectancy at birth for someone who lived in the Paleolithic was about 25 years old, maybe getting as high as 30. 

When thinking about these ancient life expectancies, the difference between life expectancy and life span is really important. 

The fact that life expectancy was around the age of 25 to 30 didn’t mean that 25-year-olds were the equivalent of 85-year-olds today. 

What it means is that a large number of children never reach adulthood. If you have two people, one who dies at the age of 1 and one who dies at the age of 70, then the average is 35. 

While we know that infant mortality was much higher in the distant past than it is today, we aren’t exactly sure how high it was. 

There is disagreement on how to interpret the archeological evidence. The evidence of high infant mortality comes from the large number of infant skeletons compared to adult skeletons that have been found. 

One estimate places the infant mortality rate in the Paleolithic as high as 40-50%, which, if true, is actually quite astonishing. 

However, another theory holds that while infant mortality was indeed high, the number of infant remains is more a reflection of high fertility. 

If you did manage to reach adulthood, then your odds of making it into your 40s or 50s weren’t bad. 

However, getting to what we call old age today was possible but not probable. That is because there were a host of things that paleolithic people had to worry about that we don’t today. 

One of the biggest ones was homicide. Evidence for this varies widely depending on where you find remains, but there are some places where the percentage of human remains that show signs of blunt trauma is over 50%. 

We like to think of nomadic hunter-gatherers as people who lived in a peaceful state of nature, but the evidence indicates that that was far from the case. 

Based on data derived from unearthed human remains, many estimates place the rate of homicide as high as 20% and, in some places, even higher.  That is one in every five people whose life came to an end at the hands of another person. 

To put that into perspective, the odds of being killed by someone else, even in the places with the highest murder rates in the world today, are well below 1%.

High rates of violence have been observed in other hunter-gatherer people over the last 200 years. 

One of the other major threats constantly looming over ancient people was starvation. A tribe of people would never be more than a bad hunt away from not having any food. 

A hard winter, a hot summer, a flood, a volcanic eruption, or any number of things could cause game to flee, making life difficult. 

One other thing observed in hunter-gatherers that probably existed in Paleolithic people was parasites and infections. These are conditions such as ringworm, hookworm, and other infections from cuts and scratches. 

One thing that ancient people probably did not suffer from is communicable diseases. 

Many of the worst diseases that have plagued humanity come from domesticated animals. Prior to the domestication of animals, that vector of disease transmission wouldn’t have existed. There is no evidence of smallpox, cholera, bubonic plague, or other diseases. 

Moreover, because people lived in smaller nomadic groups, there wasn’t as much contact between groups, so communicable diseases couldn’t easily spread.

Going from the Paleolithic into the Neolithic and into the advent of agriculture and the rise of civilization, something surprising happened to human life expectancy… stayed pretty much the same. 

The rise of agriculture and the development of complex, large civilizations didn’t result in a marked increase in average life expectancy. 

You would think that agriculture would have resulted in an increased life expectancy, but it didn’t in any noticeable amount. 

What did happen was a shift in the threats and dangers that humans faced.

Starvation remained a threat, but it was now a different threat. In the past, you might have had a bad hunt, but if the game wasn’t around you, your clan could just move.

With the rise of farming, there was still the threat of a bad crop. Now, pestilence and flooding were threats, and when a crop was bad, you couldn’t get up and move. However, you could store grain for use when you did have a bad crop.

Interpersonal or inter-tribal violence decreased with large states that could use the monopoly of violence to keep the peace. 

However, large-scale violence in the form of wars and conflicts between organized armies increased. 

When nomadic tribes fought each other, it was usually over scarce resources, and fights were often about extermination. With agriculture, most fights were about conquest. You didn’t want to wipe out the farmers because they grew the crops that you could tax and demand as tribute, which built your wealth. 

Communicable diseases proliferated as humans became settled and lived in closer proximity to animals. Trade routes transmitted diseases over wider areas, and the first epidemics and pandemics became possible. 

Childhood remained as dangerous as ever. We have even better data from the last two thousand years, and there is a consistent pattern across pretty much every civilization. 

Child mortality remained near 50% in Rome, Egypt, China, Peru, Medieval Europe, Aztec Mexico, and many other cultures. 

High child mortality remained the norm almost everywhere in the world through the 18th century. 

As such, human life expectancy remained in the low 30s all the way up to the beginning of the Industrial Revolution. 

Life expectancy did go up a bit in Europe after the Renaissance, but not dramatically. Life expectancy was still closer to what it was in the Paleolithic than it is today but may have gotten as high as 35 or 37. 

Things began to change somewhat in the industrialized parts of the world beginning in the 19th century. However, again, the change wasn’t dramatic. 

There was still a lot of squalor, living conditions were poor, and life in rural areas was very much the same as it had always been. 

By the start of the 20th century, the global average human life expectancy was still hovering around 30 years of age despite moderate gains in the 19th century. 

Then, something started to happen in the 20th century. Life expectancy began increasing……and increasing dramatically. 

The rise in life expectancy wasn’t evenly distributed around the world, but things did go up almost everywhere. 

By 1950, the global life expectancy across all countries had reached 54. 

By 2020, the global average had reached the age of 73. 

By the 21st century, a human born on the planet Earth would live over twice as long as one born just 100 years earlier. This was after thousands and thousands of years of little to no improvement in life expectancy. 

The place with the highest life expectancy today is Hong Kong at 85.3 years, and the country with the lowest life expectancy is the Central African Republic at 54 years. 

But a person born in the Central African Republic today will live almost twice as long as someone born in England in 1900. 

This increase in life expectancy was the driving force behind the rise of global population levels throughout the 20th century. It wasn’t because more people were being more; it was because more people weren’t dying.

So, what happened?  Why did humans start living longer after tens of thousands of years? 

There isn’t one single reason. There were a host of reasons which alworked in conjunction with each other. 

One of the first things had to do with the spread of sanitation. If you remember back to my episode on sewers, people in cities used to live amidst filth. 

Sewers, indoor plumbing, and flush toilets were all innovations that improved cleanliness. Improved cleanliness cut down on a major transmission vector for the spread of diseases. 

One of the biggest things, overwhelmingly so, was the development of the germ theory of disease. 

I’ve covered many stories that led up to the development of the germ theory of disease in previous episodes. Ignaz Semmelweis learned the lifesaving benefits of just washing your hands. 

John Snow managed to stop a cholera epidemic by identifying tainted water. 

Louis Pasture figured that you could kill germs through heat. 

I can’t stress just how important the germ theory of disease was because it was the key that unlocked how to treat and prevent diseases. If civilization were ever to collapse, maybe the one bit of knowledge we preserve is that germs cause disease. 

Working conditions improved, which cut down on workplace accidents, and the improvements in safety eventually found their way to safety in consumer products. 

Vaccines were developed that were able to stop many of the diseases that caused high child mortality. Smallpox, arguably the deadliest disease in history, was completely eradicated through vaccines. 

Antibiotics made it possible to treat many of the most common illnesses that affect people. 

Food production increased dramatically, all but eliminating the threat of widescale famine today. 

Despite two of the most horrific wars in human history in the 20th century and many other lesser wars, deaths due to violence decreased dramatically. 

Energy usage increased, which is highly correlated with standards of living. This was used for many things, including preserving foods through freezing and refrigeration. 

Of course, I haven’t even mentioned the improved medical care, techniques, and pharmaceuticals. 

A baby born today in all but the poorest countries has a 99% chance of reaching adulthood compared to a 50% chance just a few centuries ago. 

This has all resulted in a compressing of the gap between life expectancy and the possible human life span. 

There are still significant advancements to be made, including increasing life expectancies in developing countries, but even there, things are improving. 

As I said at the beginning, now is the best time to be alive. 

All of us have the best odds ever of living a long, healthy, and productive life.