During which periods in history, or pre-history, did the global human population decline? There are many instances of decline of certain nationalities or ethnicities, but what about the total global population?
There is Toba catastrophe theory, a super-volcanic eruption about 73,000 years ago that may have reduce the human population to around 10,000 people.
Here is a picture comparing Tobawith other eruptions.
Do black death and WW II count?
also WW1/flu outbreak
The Plague of Justinian was part of a worldwide plague, possibly triggered indirectly by cold weather in 535-536, in turn possibly triggered by an eruption of the Krakatoa volcano.
I read Catastrophe: A Quest for the Origins of the Modern World by David Keys, which attributes many 6th-century events to this cause. (I’ve wanted to reread that fascinating book, but it got lent and mislaid. )
Here’s a chart combining many estimates of world population since 10,000 B.C.:
It appears that the only significant drop in world population in this time period was during the Black Death, when the population was less in 1400 A.D. than it was in 1340 A.D. The other things people have mentioned so far (the total deaths in World War II, the flu epidemic after World War I, the Plague of Justinian, etc.) certainly slowed down the growth of world population, but there’s no evidence that population totals dropped in any significant way. The Toba catastrophe happened long before 10,000 B.C., of course.
I’d be interested in reading any “cite” that any of the estimates shown before, say, 1400 are anything but fanciful interpolations or extrapolations.
I think it’s quite difficult, but possible, to roughly estimate European population at various rough periods. To detect losses of specifi plagues and extrapolate them worldwide? Not so much.
(BTW, a week ago there was a related thread asking about an odd population decline ca 400 BC. I demonstrated that this was a lazy statistical artifact. My post was ignored. Wrong explanations for the false decline continued to trickle in to the thread. 
:smack: )
septimus, why did you reply to my post with your objection and not to all the other posts? The other posts pointed to specific events and claimed that they caused a decline in population with no numbers or citation at all. I pointed to a source that correlated a number of different studies, each of which had done some research. Is it possible that each of these studies is not accurate? Of course. Is it possible that the attempt to correlated all of these studies is not accurate? Of course. I at least attempted to find some studies that looked at all of history since 10,000 B.C., rather than just naming a few isolated events with no population numbers attached.
I don’t have a whole lot of faith that anyone can accurately estimate the current world population. The idea that estimates for thousands of years ago are anything but WAGs seems ludicrous to me.
The other posts pointed to events that might have caused a decline in population. No numbers were provided because any would be wild-assed guesses.
You linked to wild-assed guesses and suggested they might have merit. I suggest otherwise.
HTH.
I like to debate ideas, and often ignore poster identities. Your response here seemed peculiar enough that it jogged my memory. You don’t like me.
I think this is one of the silliest and least appropriate responses that’s ever been directed against me at SDMB. I did respond to it in that thread, pointing out the charge of “career-related motives” was one made by linguists. I’m curious: Were you in a funny mood that day? Or do you still feel that your response was appropriate?
Some points to make on estimating population, losses, etc.
Barbara Tuchman, in A Distant Mirror, says all the research on the Black Dath gives only the wild-ass guess that between one third and one half the population of Europe died. Presumably Europe and the Mediterranean were ideal for the Black Death since they harboured fleas and rats.
Those are less likely to spread the disease like wildfire in less populated, less crowded areas, but best guess is the disease did arrive on trading vessels from the east.
Similarly, when the president of France was talking privately and frankly with Mao Tse-Tung, he asked him what the population of China was, and Mao said something to the effect of " about 1.1 to 1.4 billion. We don’t know for sure because provincial officials exaggerate their populations to get more of the grain quota."
Any estimate is going to be no btter than the input data, which for most of history will be simple hand-waving.
Back on topic. It is completely true that estimates of past populations are little more than WAGs. The column in that Wikipedia chart by Biraben seems completely wacko. What could possibly justify an increase of 1 million in the world population between 0 and 200 AD? That’s implausibly precise. Then there’s a decrease of 50 million between 200 and 400. Then 500, 600, and 700 are 206, 206, and 207 million. There may be a justification for the world population to be stable for hundreds of years but again I can’t understand any assumption that would allow for an increase of 1 million. Without seeing the original paper, which I couldn’t find, I would be very leery about accepting any of those numbers.
That paper was from 1979 (1980 is the date of the English translation) and none of the newer ones try to cover as many mileposts. That may be because scholars are less apt to make stabs at these numbers. It’s only been in that time that estimates of the population of the Americas have soared, although those are still the subject of enormous battles between the highs and the lows. I’d say that the trend worldwide has been toward ever-larger population estimates for the past, especially in non-Western areas where modern archaeology has only begun to get results out to the community. There was definitely a Dark Ages bias and a similar bias that non-westerners couldn’t have had European sized cities in earlier work. Most of the research I’ve seen has gone toward correcting that and recognizing the amazing feats of complex societies in other parts of the world.
I think the wild ass had been hunted to extinction by then, however.
A Distant Mirror is a great book but it’s 35 years old and therefore based on research that’s even older. I didn’t see this when I posted but the same objection holds: don’t trust anything on population statistics that old. Any numbers might still be true but that would be purely fortuitous.
Her point was not numbers, but that any number quoted was incredibly imprecise and probably unknowable - a timeless message on this topic unless there’s been some serious progress on the 1350 European census.
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