>They were rare when the average age of death was like 30.
When lots of people died before their first birthday‡, the average age being thirty meant that lots of people who made it past their first birthday would live longer than thirty.
‡Estimates vary from 30 to 50% rate, in the old world.
I really wasn't trying to throw a stick in the mud in terms of a hard scientific date which is why I phrased it how I did. That said my reference wasn't so much toward "the old world" which I take to mean in the last few thousand years but rather on more of an evolutionary scale, that is millions of years ago.
When lots of people died before their first birthday‡, the average age being thirty meant that lots of people who made it past their first birthday would live longer than thirty.
‡Estimates vary from 30 to 50% rate, in the old world.