John Francis wrote:
On Mon, Oct 03, 2005 at 02:12:08PM +0200, Toralf Lund wrote:
John Forbes wrote:
I suspect Toralf is alluding to the fact that more than half of the
human beings who have ever lived are still alive today. As they
haven't yet died, we cannot be certain that they will. (This is very
worrying.)
Exactly ;-)
Except that it's not a fact - just a common misconception.
Around half the people who have lived to age 65 or over are alive today,
but that's not the same as saying half the people who ever lived are alive.
2000 years ago the world population was roughly 200 million.
[ ... ]
Taking those corrections into acount it's apparent that not even half
the people born in just the last 2000 years are alive today, let alone half
the people who ever lived.
Actually, what I've heard is that somewhat *less than* half of the
people who ever lived is alive today. That may also be an exaggeration,
but I would guess that it is not so much a "misconception" as a somewhat
simplified picture drawn to illustrate what exponential growth means.
The thing is, the population *was* relatively flat until 1900 or so.
Actually, it had grown to something like 1 billion, then, but a rise
from 200 million to 1 billion in 1900 years is *nothing* compared 1 to 6
billion in 100 years. And there were some significant drops on the way,
too, like after the black death... All in all, the notion may not be
*that* far away from the truth - again, that's exponential growth for you...
But it's just a somewhat amusing piece of statistics, anyhow...
On a related note, another common misconception is that nobody did live
to the age of 65 a few hundred years ago, because the life expectancy at
birth was 40 or whatever. The truth is that the main contribution to the
lower life expectancy was a very high child mortality rate - the chance
of getting old *if you survived childhood* wasn't necessarily that much
lower than today.
- Toralf
