In this article, About.com article on Life Expectancy they claim:
In 1900, the world life expectancy was approximately 30 years
I've also the same claim elsewhere.
However, this doesn't jibe with informal data-gathering I have done:
An arbitary search of Wikipedia of random people that I know lived and died (of natural causes) before the 20th century shows that almost all of them died over 30.
I was in an old cemetery the other day, and saw that very few of the people buried there pre-1900 was under 30 years.
So I understand my "research" is purely unscientific - e.g. to be on Wikipedia you have to be famous, which means you probably were wealthy, which means you probably increased your chances of living longer.
Still, I find it hard to imagine a world where 30 is the life expectancy - i.e. that roughly around half the people would die younger than 30.
I would like to hear further evidence supporting this fact or explanation for the fact.