Life expectancy might not be what you think it is. Life expectancy is average expected lifetime at a particular age. We usually talk about life expectancy at

Life expectancy might not be what you think it is. Life expectancy is average expected lifetime at a particular age. We usually talk about life expectancy at birth. If a population has a high infant mortality rate, then life expectancy at birth may be 40, but life expectancy at 10 years of age might be 70. I can't name a source off hand, but I believe I've read that infant mortality is a large factor in low life expectancies. In other words, we may not have significantly increased lifespans, and may have simply solved the major infant mortality problems.