Has human life expectancy changed through the ages, and if so, how do we know?

Question

What are reliable sources of data for this?

Answer 1

Here's an article in Wikipedia about life expectancy throughout human history. I suppose they know from records kept (from ancient Greece onwards). Or from bone examination in more ancient times.

Answer 2

Yes, life expectancy has changed.
The cemetery's a good source. However, this is only a trend for a few centuries. Given stochastic events, and the length of human existence, it's important that we be able to track age throughout history.
One of the best methods is with Carbon dating. Carbon-13 decays with a constant rate to C-12. When ancient humanoid bones are discovered, you can use this ratio to determine how long ago that person was alive. Then, you can do modern-day bone/teeth analyses to determine approximate age. Thus, you can find both when the person lived and how long he lived.
Life expectancy differs for people in different countries. This is somewhat of a real-life experiment. In those places with poorer nutrition, people just don't live as long. Where there is an abundance of good food, however, people who take care of themselves can live much longer. The countries with poorer nutrition are kind of like more ancient times. People used to have to rely on whatever the soil provided, before agriculture was invented. Exercise was not a problem, as they spent much time hunting and gathering. Thus, we can make a correlation between food quality and life expectancy.

Answer 3

Yes,

Visit a graveyard from the 1700s, 1800s, early 1900s, and today. Record the birth and death date of those buried and figure out how long they lived.

Then calculate / graph the average lifespan for each century. There is your reliable source of data.

Answer 4

Good answers here. Just made me think of infant mortality rates, since my great-grandparents had a few babies that died in infancy.

The state I grew up in has rather low life expectancy, while it's common for people to live past 90 where I live now. I think there are a variety of factors that are involved, mostly environmental. Come to think of it, there are a lot of farm families here, so maybe their stress level is lower than those who live in a busy city.