The college students in the course I teach about the Black Death are asked if they are a farmer or a nun. What would their lives have been like if they had been affected by this terrible disease?

Setting aside how they envision what it would be like to fight the plague, these undergrads often think that they will be considered middle-aged or elderly by the time they are 20. They don't think they'd be in the best shape of their lives.

They're reflecting a common misconception that long life spans in humans are very recent and that no one in the past lived past their 30s.

That isn't true. I study human skeletons from archaeological sites to understand what life was like in the past. The Black Death hundreds or thousands of years ago was linked to fertility,mortality, and migration. Some people do not live long lives, but there is evidence that many people did.

The length of a life is recorded by bones.

Estimating how old people were when they died is one of the first things researchers do. Information about your teeth and bones as you get older is used by bioarchaeologists.

Changes to joints in the pelvis are common at older ages. Observations of these joints allow us to estimate ages for people from archaeological sites with joints that look similar.

A microscope can be used to count the cementum on teeth every year. It's like counting a tree's rings to see how long it's been there. Many studies have documented the existence of people who lived for a long time.

Most people who lived in the city of Cholula in Mexico between 900 and 1531 lived past the age of 50.

There are a lot of examples from historical records of people who lived a long life. The sixth-century Roman Emperor Justinian I is said to have passed away at the age of 83.

Our species has experienced long life spans for at least the past 160,000 years, according to analysis of the tooth development of an ancient Homo sapiens person from Morocco.

Old age isn't a modern phenomenon – many people lived long enough to grow old in the olden days, too
Population numbers in 2019. Credit: Chart: The Conversation, CC-BY-ND Source: Get the data

A mathmisunderstanding is being cleared up.

Many people lived long lives in the past, so why do people still think that everyone died by the age of 40? There is confusion about the differences between life spans and life expectancy.

An average number of years of life remaining for a person is called life expectancy. Life expectancy at birth is the average length of life for newborn babies. The life expectancy is how long people will live on average.

In medieval England, the life expectancy at birth for boys was less than three years. Medieval England's life expectancy was 25.7. People who celebrated their 25th birthday in that era could expect to live until they were 50.7, on average, more than two decades later. Many people would have lived much longer, into their 70s, 80s and even older, if this was an average, since it is.

A huge variety of people with very different health conditions and behaviors, some who die at very young ages, some who live to be over 100 years old, and a lot whose life spans fall somewhere in between are reflected in life expectancy. Life expectancy is not a guarantee about a person's life span.

Some people don't realize that low life expectancy at birth is related to high infant mortality. There were deaths in the first year of life. Given that life expectancies reflect averages for a population, a high number of deaths at very young ages will skew calculations of life expectancy at birth. People who make it past the vulnerable infant and early childhood years can expect to live a long life.

Life expectancies can be increased due to advances in modern Sanitation and vaccinations.

Consider the effects of infant mortality on overall age patterns in two populations with vastly different life expectancies at birth.

Infant mortality in Afghanistan is high, with almost 105 deaths for every 1,000 children born.

Infant mortality in Singapore is very low, with only two infants dying for every 1,000 who are born. People in both countries live to be very old. Fewer people survive to old age in Afghanistan because there are more deaths at young ages.

It's possible to live a long life.

Long lives are not a distinctive characteristic of the modern era.

It might help you feel more connected to the past if you know that many people have lived long lives in the past. You can imagine grandparents in Neolithic China or Medieval England bouncing their children on their knees to tell them stories of their own childhoods. People who lived long ago may have more in common with you than you realize.

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