I saw this number proposed in a recent book and wondered what human population studies it might be based on.
2006-09-15 18:06:41 · 6 answers · asked by LaBrat 3 in Social Science ➔ Anthropology
You would need 2 sets of data. 1. Historical world population for different time periods and 2. avg life expectancies for those time periods.
I did some quick back of the envelope calculations to see if 100B sounds feasible.
1. There are currently about 6.5B on earth today.
2. The population in 0 AD was 300M. The population in 1000 AD was 310M. Assuming a life expectancy of 20 yrs, that would equal about 15B people in this time period, (300+310)/2/20yrs*1000yrs
You're basically calculating how many people are born each yr * the number of years in the time period.
3. The population in 1750 AD was 790M. Again, assuming a life expectancy of 20 yrs, that would equal another 20B people between 1000 AD and 1750 AD.
(310+790)/2/20*750yrs.
4. The population in 1950 was 2.5B. assuming a life expectancy of 30 yrs for the period 1750-1950, you get another 11B people.
(790+2500)/2/30*200
That's over 50B from 0 AD to current day. Modern man has arguably been around since as recently as 10K BC. So you have about 10,000 yrs to account for the other 50B, which I think sounds reasonable. At the very least 100B sounds about in the right ball park.
I included a link to world populations from 0 AD to current. I was unable to find a decent chart about average life expectancies, I'm relying on sparse data points, just my own personal knowledge that the world's life expectancy was about 30 to 35 yrs in 1900.
Recalculating what I've done with more yearly population data points and more granular life expetancy rates would yield a more accurate answer. But like I said, I think the back of the envelope estimate gets you in the ball park.
2006-09-15 19:00:06 · answer #1 · answered by obiwin 2 · 1⤊ 0⤋
Most of those people are from recent times, which is always the case with exponential growth--that the more recent time periods pretty much swamp all the earlier population sums.
2006-09-15 20:57:26 · answer #2 · answered by A professor (thus usually wrong) 3 · 0⤊ 0⤋
Actually, it's true, yeah. We are replaced (the entire population of Earth), completely, approx every 100 years.
2006-09-15 22:16:14 · answer #3 · answered by Boliver Bumgut 4 · 0⤊ 0⤋
They might've gone a statistical analysis of population growth over time- & just counted backwards... I'm sure there's some kind of mathematical formula one can use to figure it out.
2006-09-15 18:13:21 · answer #4 · answered by Joseph, II 7 · 1⤊ 0⤋
probably based on all humans that have lived and died throughout history since there is about 6 billion currently
2006-09-15 18:08:40 · answer #5 · answered by d2pain 3 · 0⤊ 0⤋
i think this study was based on a cheeseburger. i'm pretty sure it had pickles, though.
2006-09-15 18:08:41 · answer #6 · answered by Anonymous · 1⤊ 0⤋