Today Toba[1] is huge volcanic lake with a central island, and a sort of washed out station on the later hippy trail, but still physically interesting to explore. For anyone considering a visit to Sumatra, do check out the nearby taxidermy museum in Medan[2]. It's absolutely incredible. And for surfers, don't miss the island of Nias[3], but fly instead of getting the boat in bad weather, which amounts to a moving vomitorium. Southeast Sumatra has a huge area of largely unexcavated stone ruins to rival Angkor [4] from an ancient, regionally significant civilization and sea power, Srivijaya[5].
My ex-wife was getting her Geology BA when we got a new dog. We thought “Toba” would be a great name. It wasn’t, she tried and tried to live up to her namesake.
It isn’t easy to travel by road but flights are cheap. On the other hand if you go by minivan you will see so much more Sumatra...
Sumatra is suprising - mountains, pine forests, mild climate suprisingly for equator it could often get chilly. Lots of agriculture. Vivid nature. But real jungle and primary forrest is mostly gone.
People are friendly, smiling, easygoing and welcomming to foreigners. Lots of people speak a little English and bahasa is quite easy to pick up. No grammar, super simple.
Indonesia has almost worst education system in the world [1] and forward thinking isn’t part of the culture. Neither is working hard. That can put you through lots of hardship - if you care.
People are incredibly social - this is what their life is about. There is a lot of childish fun everywhere - when minivan is passing through the village local people pour buckets of water through open windows. Lots of people sing and play guitar - most badly in my opinion but it is still sweet.
People are honest, you can trust strangers, not much of small crime, petty theft is uncommon etc.
Everyone smokes cigarettes everywhere also on the bus. Even 4 year old could be already hooked on fags. [2]
There is a lot of people, it is quite overpopulated island (not like Bali but close). It means tons of trash everywhere, everywhere, terrible impact on environment. Indonesia is world largest producer of marine pollution (3.2 milion metric tones of plastic per year). [3]
If there is trash it is mostly burned on site (including plastic et all) so you get a haze. Cities are polutted, there is too many cars, people and not enough infrastructure. Medan - largest city in Sumatra and 2nd largest in Indonesia is the worst place in SE Asia in my opinion. It is just hudge, poor, dirty and without anything there to compensate.
Clean water, sewage’s treatment forget about it. Everything goes into rivers and ocean. There is now wild gold rush which is destroying riverbeds in Sumatra.[5]
The food is good but monotonous.[4] The hotels, homestays, peningapans are usually quite dirty. Regarding cleanliness Thailand it is not. Don’t expect clean sheets. Bedbugs are common. There are exceptions.
Definitely go to Sumatra.
Disclosure: I have spent mist part of last four years here.
> But our looming weight makes us vulnerable, vulnerable to viruses that were once isolated deep in forests and mountains, but are now bumping into humans, vulnerable to climate change, vulnerable to armies fighting over scarce resources. The lesson of Toba the Supervolcano is that there is nothing inevitable about our domination of the world. With a little bad luck, we can go too.
I'm personally more inclined to think we are less vulnerable than ever before.
I doubt any virus would wipe out an entire population. An infectious agent spreads better among a numerous population, but as it kills its hosts, the population becomes smaller, which slows the infection rate. So there is negative feedback here, and I doubt that can lead to a total extinction of the host species. Not to mention that we have modern medicine now, and that we understand how viruses work.
Climate change is an issue, but I have hard times imagining how it could wipe out all human beings. Worse case scenario, I guess, would be a sharp decline in agricultural production. So hunger riots and stuff. But even that would at worse reduce the population until a new equilibrium is reached. And I don't see that equilibrium to be at 0.
Nuclear war is a serious threat. But it's not like it would destroy the surface of the Earth or anything. It would provoke a nuclear winter though. I suppose a nuclear winter is about as bad as a volcanic winter is, or worse. Again, the main difficulty would be a sharp decline in food production. And that also would require a new population equilibrium to be reached.
IMHO human beings, nowadays, can deal with an awful lot of contingencies. We can predict them, we can store resources, we can plan ahead...
There really is a case to make about the idea that humans will survive a mass extinction. Annalee Newitz wrote a book about it[1]
I'm not sure "humans will not go totally extinct" is any more comforting than the cliche of "We'll not destroy the earth, it'll be fine, it's human's that'll be wiped out" there's definately the opportunity for a lot of people to have a very bad time. Even worse than the bad times that large segments of the planet are experiencing right now.
No matter how bad times large segments of the planet are experiencing, there have been worse times. Meaning:almost all of the past was worse than it is today.
At https://ourworldindata.org/ you can find tons of data, info-graphics and articles from various (respectable) sources backing that claim. That's not meaning that things are all rosy yet - just meaning that they have been worse in the past!
I feel like people use the current ok state of humanity and the phrase "it's been worse!" to block out a completely unrelated statement, "it might get worse".
I never said that we not better make sure that it stays that way.
If I see someone mentioning the "current, miserable state of the world" I have to object and correct their skewed view (which is not of the present but of a wrongly remembered or romanticized past that serves as incorrect baseline for the comparison!).
I think it's not so much a rosy view of the past, but a fear-filled view of the present.
I did a quick poll of my FB feed, and about 60% of my "friends" felt that the present was worse than the past. Despite all the evidence saying that it's not.
I'm also not afraid of isolated viruses in desolate places. They have limited gene pool and no humans to practice with. It's incredibly unlikely that such virus would randomly be very very good at targeting humans, but also very very bad at staying super sneaky when on a human host.
The optimum strategy for virus is not to kill. It's to stay unnoticed and spread. And the best way to stay unnoticed is not to cause any symptoms ever.
HIV is scary because it's not very good at staying unnoticed. But it's also very bad at spreading too. Same goes with anthrax and pretty much every other deadly virus/bacteria. They typically are optimized for other mammals and therefore they suck at both staying unnoticed and targeting humans.
As a species we're still part of the food chain, we depend upon plants and animals to survive, and we're full of microorganisms. Some of the long lasting consequences of the Chernobyl disaster in this respect are quite worrying - https://www.smithsonianmag.com/science-nature/forests-around....
> Other events (if in the next decades) that might kill billions of humans:
>
> - meteorites.
No asteroid large enough to kill billions of humans is likely to impact Earth in this century. After that, it's likely that humanity will be so advanced that it'll be able to either mitigate or deter an impact of any magnitude.
An overlooked possibility imho would be a catastrophic population decline[1]. Basically women not having children anymore. Japanese style, only worse.
It's difficult to imagine it leading to extinction, since there will always be groups, at the very least religious groups, who will keep having babies. But still, it wouldn't take much of a cultural change for it to expand to all women.
Not saying it's plausible, but to me in terms of population dynamics it's at least as much of a concern as climate change (by this I mean that I believe reproductive behavior will have more impact on demography than climate change).
There is _massive_ evolutionary pressure going against this. To the extent that not wanting to have children is at all genetic, it will disappear from the gene pool within a few generations.
That the desire to "not want to have children" (especially among women) exists at all is caused by the sexual revolution (contraceptives), which changed who had children from "people who desired sex" to "people who desired to have children."
Maybe contraceptives are a dead-end against which evolution can't do much.
Maternal instinct exists : it pushes a woman to keep her offspring alive at all cost. I suppose it also makes women yearn for having a baby to take care of. But apparently, having just one is enough for them. Maybe two, but they seem to be content with no more than that.
What makes a woman pregnant in the first place is the sexual impulse of the male. That sexual impulse is the primary way nature gets animal organisms to reproduce. With contraceptives, males can satisfy that sexual impulse without creating new offspring. How will nature induce highly-intelligent animals to make an offspring if the sexual intercourse is no more sufficient? It's hard to imagine how genes could intervene high enough on cognitive functions to induce a thought such as "I must have intercourse with this women without contraception because I want children".
Well, no rule is written in stone. What you talk about could be a consequence of the fact that men and women are more or less built the same way after all. Kind of like why men have nipples, even if they are useless to them.
My point remains anyway : even if there was a perfect symmetry in gender roles, parenting instinct would be what makes parents desire to have at least one offspring and keep it alive at all cost, but what would drive them to have more than two would be sexual impulse.
I don't understand : we are in the middle of the biggest population explosion in the history of the world and at the back end of a century of government programs aimed at reducing childbearing...
Most of the population explosion is behind us. Many developed countries have sub-replacement fertility, and it seems to be a trend followed by developing countries.
"As of 2010, about 48% (3.3 billion people) of the world population lives in nations with sub-replacement fertility."[1]
Complex behavior can be and often is genetic. A great example of this is the vastly different behavior of the zebra and lion when in close company with zebras. The zebra will engage in herd behavior, whereas the lion will try to eat one of the zebras. No amount of socialization can alter these behavioral patterns.
I can tell you that my wife and I both knew long before we were anywhere near adults that we wanted families. You know how some people know that they want to be a fire fighter or a police officer when they grow up? I knew I wanted to have a bunch of kids. The story is more or less the same for her. And my wife and I both grew up on the left, where the attitude toward having children varies from something you do after you have your career sorted to outright anti-natalism.
> . A great example of this is the vastly different behavior of the zebra and lion
We're not zebra and lions
> knew long before we were anywhere near adults that we wanted families
peer pressure is strong in our society
family is a motivation to stay alive for many
> I knew I wanted to have a bunch of kids.
Yeah I though I knew as well, much like I thought I was going to be an astronaut
Now I'm a grown up man, in charge of his life, and I know I don't care about a family
And it's not the gene's telling me, I still think about having a legacy, a mini me persisting my DNA but I know that it's just a legacy from the past where a man without a family to support wasn't a real man.
That's it, education and culture
If reproducing was such a strong genetic trait, men on heart would have been billions centuries ago
The truth is kids are family support, the more societies get rich, the less people make children
It's scientifically proven, poor need kids not for reproduction but for elderly support
Poor also make a lot of children because in poor societies kids die more easily
For all of human evolution except the last 50 years, so 6,997 out of the last 7,000 generations, the drive to have sex was synonymous with the drive to have children. Then we invented birth control. Now evolution will select for people who have a desire to have children, separate from their desire to have sex.
The idea that complex behavior can be caused by genes in animals, but somehow not in humans is incorrect. People point to culture as if it is some magical force that makes people do things, but the human ability to create and interact with culture is itself the result of genes. After all, zebras and lions don’t have culture.
And you missed my point: I grew up in a culture that did not value having children. Having children was considered an after thought, something to be done after you had attended to your career. Growing up, I only knew one family with 4 children. They were considered the weird religious family. Yet I have known since I was 12 or 13 that I wanted to have a large family, even though I grew up in a culture that would look down their noses at a family of 4 or more children.
And the argument that poor people have lots of children for financial reasons doesn’t hold up any more. It did when most people were farmers, but the poor in the developed world are no longer farmers and I don’t think there’s any way to argue that children are a net financial benefit to them.
Citation needed - obviously culture and education have an enormous impact on how humans live, but given that other animals are driven to reproduce, it shouldn't be a surprise that we are also.
> There is _massive_ evolutionary pressure going against this. To the extent that not wanting to have children is at all genetic, it will disappear from the gene pool within a few generations.
This is only the case if the selection pressures which humans in the developed world are facing stay the same. Since they seem to be tied to our technological development, I think there is a good argument to be made that these selection pressures will intensify as we breed resistance to them. My personal theory is that the increasing addictiveness (see the PG essay on this[0]) of modern life is why people are having less children. I don't see that trend changing.
I do think there's a good chance that technological renunciation and voluntary cultural isolation of some sort are the best solution to this problem for people who are naturally susceptible to the addictiveness of modern life.
Based on what I've read, pre-agricultural people nursed their children until the age of 4 or 5 when they could keep up with the tribe on foot, which limited the birth rate. The explosive growth in population we have had for the last few thousand years dates to the agricultural revolution, when we settled down in one place which allowed women to wean their children sooner and have more. So in a sense the absence of birth control is the new and unusual phenomenon here. If you look at ratios of sexual activity to pregnancies human beings are extreme outliers- we clearly are evolved to use sex for bonding first and reproduction second, so the idea that birth control is going to change our behavior through selection pressure seems wrong.
I can not imagine that lack of babies could ever become a problem for humanity until humans decide to build humans so that the "natural human species" dies out.
The solution for the aging population:
- Automation.
- Biochemical solutions and genetic engineering to remain/become capable. Replacement of natural body parts by machine body parts.
Worrying about overpopulation is short-sighted. Also, no matter what kind of problems overpopulation brings, it's hard to imagine how that could lead to extinction, which is what we were discussing.
Overpopulation is frequently the cause of steep popuation decline (90+%) in ecology due to input resource depletion and the building of toxins that are the end products of that species metabolism.
Pollution and resource scarcity are the obvious limits that can send population numbers off a cliff.
I would view the comfortable lives of humans in the developed world as a very peculiar circumstance, not as something which will persist as the norm. Life expands to consume all available resources. Humans are part of the lineage that we call life. That we are poorly adapted to modern life is just a temporary state of affairs. Though many people are opting out of large families, not all are. And the people who aren't are the future of the species.
At space there are some pan-galatic killers, nearby supernovas (no idea where is the closest candidate), and a black hole could always cross our path without any warning.
A black hole crossing our path would give plenty of warning, assuming it approaches significantly slower than the speed of light.
The effect of a black hole's gravity on distant objects is exactly the same as the effect of any other object with the same mass. It would disturb Kuiper belt objects that everyone's watching very carefully these days, affect the orbits of the outer planets as it moves closer, and bend light around its event horizon in a very obvious way.
Whether we can do anything about it, of course, is a different problem.
We're pretty good at disease control, see eg. the recent ebola outbreak. An outbreak of anything dangerous would be quickly contained. There are no organizations with the capacity to surreptitiously produce, distribute and release an infection agent broadly enough that it might kill in the billions before being contained.
That basically leaves the US or Russia (the only countries with the capacity to do so) arbitrarily deciding to nuke most cities in south Asia.
I'd give China more of a chance than Russia, actually. They have more resources. (But perhaps less willingness than Russia: China is doing very well with the status quo.)
I don't think China has the nuclear warhead stockpile to kill 1 billion+ people. Wikipedia says "Current stockpile (usable and not): ~260" which means each would have to kill 3.8 million, which basically means delivering each perfectly into a major city. That's a non-trivial operation to put it mildly.
That said, I don't see any objective (rational or otherwise) of either country that would be advanced by such an attack. And again, we're talking about an attack that will kill 1B+ people, not just any nuclear attack -- that's a different story. Still low probability, but at least there are semi-rational objectives that could motivate it.
Oh, I didn't mean to imply the Chinese had enough stockpiles. I meant they have a big enough economy to rapidly build up their nukes (or invest in bioweapons etc), should they decide to.
Alternatively: "how human beings rose from the lesser hominids in 70,000 B.C.E."
There's a serious theory it was this bottleneck where humans were confined to environments without natural preditors (seaside cliffs like those near Cape Town) and where social interaction was a necessity. Those with higher intelligence, particularly social intelligence, would scored more mates in that environment. And thus we had a runaway intelligence arms race that separated modern humans from their immediate hominid ancestors.
Note that humans and Neanderthals diverged 400,000 years ago, and when they died out ~40,000 years ago, they were basically technologically and socially indistinguishable from humans.
So I'm doubtful the secret sauce of humans had its origin 70,000 years ago.
Some of this comes down to "what counts as secret souce"?
Did the "secret sauce" of mouse-gui originate in the 70s with Bell Labs or Apple in the 80s? Did the secret sauce of early aggricultural civilization (Hati, Sumer, Hindus Valley..) start the first time a person grew stuff for food or when a larger scale grain economy first emerged?
There is plenty of evidence that paleo-humans from well before that 70k ybp cutoff was special, unique in the animal kingdom. Knowing what we know about people, a lot of that behaviour was almost certainly cultural and probably language-based. Very complex tool use, hunting and gathering methods, shelters, fire. Perhaps even fire-aggriculture practices.
Regardless, 70k ybp (or 40 or 100) the "secret sauce," whatever it is, begins to yield fruit. There are artifacts with symbolic expression, what we'd call art or even politics. The human population grows. We inhabit more (almost all) ecological zones. People get everywhere, including australia by 40-50k ybp. Maybe earlier. Tool invention gets faster...
But species are to some extent artificial categories. Sapiens and Neanderthals were close. Genetically compatible and behaviorally similar (as far as we can tell). It would not be unreasonable to define them all as subspecies or ever varieties within a species.
Apart from the minor fact that until we knew some of us are descended from Neanderthal they were consider by everyone to be different species. Ideology 1, science 0.
It's impossible to deny that studies of our biology attracts a lot of interest, and we're not best placed for objectivity. That said, tghe splitter-lumper dynamic always exists. Are polar bears just big, white, aquatic brown bears that don't hibernate, or a species? New information about interbreeding should tip the balance in favour of subsceices. That's happening. Science works. I don't think there's an ideology problem here, at least not more than anywhere else.
Wolfs, dogs and coyotes interbreed, too. And coyotes have long been thought their own species. (They are quite fascinating: https://en.wikipedia.org/wiki/Coywolf .)
Yeah, that comment started out as "anatomically modern humans" with a caveat on later interbreeding before editing; I hope the elisions were a net gain for getting the point across, if slightly less precise.
You ever met one? Had a conversation? Assessed it’s working memory, capacity for abstract thoughts and manly layered thinking?
There is a lot we don’t know. The fact that Neanderthal buries their dead with some sort of symbolism, cared for elders, and lived in (small!) groups doesn’t really give us firm answers to these questions.
Right, I've read the same. In practice they could very well have been more intelligent than humans.
One interesting idea is that humans ultimately triumphed because we had better social connections, we traveled much further and had much larger circles.
The evidence we have for Neanderthal development is subject to precisely the same limitations to the evidence we have on the development of other hominids.
If you can't meet & talk to humans from 80,000 and 60,000 years ago, are you able to say any change happened 70,000 years ago?
Surely the Neanderthals have been subject to the same selection pressure as homo sapiens throughout the aftermath of the Toba catastrophe nevertheless... No?
Assuming the bottleneck theory is valid to begin with, this was a global ecological disaster - it's not like the Neanderthals sat this one out on another planet : )
The extinction of megafauna (eg, mammoths) didn't begin until tens of thousands of years later, so the effects at northern latitudes could not have been too severe.
That is easily disproved: Khoisan people are the earliest offshoot off the sapiens evolutionary tree - they split from the rest of us cca 175 thousand years ago, and they are behaviouraly modern in all possible ways - they have large social groups, language, culture etc, which indicates those characteristics were already evolved by 175kya.
I don't think these are necessarily incompatible theories.
First, any theories about this period (the paleo revolution and/or dispersal era in a lot of theories) are very speculative and prone to change. We just don't have that much information. So, the margins are necessarily huge.
So, both these bottleneck narratives are probably over-literal reading of the data we have, at least stated in simple forms. Either way, they point to a single small seed population. There could have been many times more people (neanderthals and sapiens) at the time and later, and they just passed on far fewer genes to 100ky later.
Yuval Harari touches on the question you raise. Sapiens vs neanderthal (and others), and at one point do human behavioural characteristics (or more precisely their consequences) emerge as different. His take is (roughly):
[1] "anatomically modern" sapiens existed for 100ky+ before these behaviours emerge. [2]Findings do not imply a big cognitive or behavioural gap between sapiens and earlier subspecies in this period. [3] there appear to be botlenecks in our lineage, dating to this period [4] The "paleo-revolution" happened in some form, and he believes it was primarily linguistic [5] Our language abilities allow flexible, large scale cooperation that is unrivaled in our clade, and did not widely exist in the lower paleolithic even in sapiens [6] he spends a lot of time on the nature of those linguistic tools. In a nutshell, advanced language allows symbolism, necessary for human-level culture. Trade. Chiefs. Tribes. Gods. Money.
All that could have happened in a single cliffside cove. That seems possible.
His argument/theory is attractive, but these things are far from set in stone. New findings will force all theories to adapt. Some will become unlikely.
Certainly the game of getting smarter due to sociality had been going on for a long time before this. But it is still quite possible that something about those survivors gave them an edge in the following centuries. And since we can't see a fast change in anatomy around then, it is a fair guess that any such change was mental.
Perhaps the confinement was the part that made social interaction necessary, if humans were stuck sharing a small area rather than expanding into the neighboring territory.
The article is mixing evidence for bottlenecks at different times. Your quote ...
> Because once in our history, the world-wide population of human beings skidded so sharply we were down to roughly a thousand reproductive adults.
... links to Hawks et al. (2000), with this in the abstract ...
> It is our conclusion that, at the moment, genetic data cannot disprove a simple model of exponential population growth following a bottleneck 2 MYA at the origin of our lineage and extending through the Pleistocene. Archaeological and paleontological data indicate that this model is too oversimplified to be an accurate reflection of detailed population history, and therefore we find that genetic data lack the resolution to validly reflect many details of Pleistocene human population change. However, there is one detail that these data are sufficient to address. Both genetic and anthropological data are incompatible with the hypothesis of a recent population size bottleneck. Such an event would be expected to leave a significant mark across numerous genetic loci and observable anatomical traits, but while some subsets of data are compatible with a recent population size bottleneck, there is no consistently expressed effect that can be found across the range where it should appear, and this absence disproves the hypothesis.
So yes, according to that study, the rest of the article is bullshit. But then, it was published in 2000.
"The world-wide population of human beings skidded so sharply we were down to roughly a thousand reproductive adults."
This is a completely mind blowing idea that humans were down to a count of about 1000 adults. Look at us now at 7 billion, and we just can't stop warring with our fellow relatives.
No sign that this is not just a temporary stop, in fact the opposite. There were periods of relative peace in world history for longer than that.
In the last 100 years we had 2 world wars, 100s of millions killed, and tons of peripheral wars during the "Cold War".
Besides for a lot of modern history wars didn't involve much of the citizenry (they had mercenary armies). Now civilians are almost fair game. And where they had arrows, spears and swords for most of history, we now have airforces and atomic bombs.
The world wars aren’t the top wars for percentage of living humans killed, and may not even be the top in terms of absolute numbers of humans killed. For example, the An Lushan Rebellion may have killed 10-15% of all humans alive at the time.
>For example, the An Lushan Rebellion may have killed 10-15% of all humans alive at the time.
Those numbers are highly discredited.
Historians such as Charles Patrick Fitzgerald argue that a claim of 36 million deaths is incompatible with contemporary accounts of the war. They point out that the numbers recorded on the postwar registers reflect not only population loss, but also a breakdown of the census system as well as the removal from the census figures of various classes of untaxed persons, such as those in religious orders, foreigners and merchants. For these reasons, census numbers for the post-rebellion Tang are considered unreliable. Another consideration is the fact that the territory controlled by Tang central authority was diminished by the equivalent of several of the northern provinces, so that something like a quarter of the surviving population were no longer within the area subject to the imperial revenue system.
What's actually gigantic and not just perceived as such though, also changes with the scale -- since we're talking about percentages.
If the earth had just 200 people, 20 of them killed is 10%, but it's nothing that a small determined fight between two tribes can't easily achieve, without even weapons.
Whereas the 3-4% of the 3 billion during WWII is a much bigger affair -- took tons of bombs, battles, war-caused famines, an extermination program, and even nuclear bombs...
And despite all that, the proportion was lower and the absolute numbers at least comparable. Deaths on an enormous scale, including lots and lots of civilians, isn't anything new to the 20th century.
From the article: "As the world becomes more interconnected, the powerful have ever more incentives to avoid the catastrophic economic consequences of going to war too. Conflict isn’t good for your economy in a world of dense trade networks and digital flows."
The exact same argument was put forward just before WWI. Then all hell erupted.
In historical terms the decline is insignificant in duration. It just marks the point from the end of the Cold War, when there remained one sole global superpower (and most of the wars in the last 20+ years, from the Gulf, to Yugoslavia, Iraq, Afghanistan, etc are wars where it fought or helped fuel). The article mistakes a decline in war during the end of the Cold War (when a global player emerged) for some long term trend.
Obviously there are more and more signs that this is not to be so -- with other players emerging like China, tension rising in different areas, even neo-fascists coming back into play in various countries governments.
Yes but in the last 100 years we've also added around 6 BILLION new people. 100 million dead is a drop in the bucket compared to the amount thats been added due to advancing technology and culture.
Those who commit war can kill a much higher multiplier of casualties than ever before, however. It would get pretty bad if there were a reason for the percentage who are fighting had a reason to broaden their scope.
It's not that "1000 reproductive adults" disproves the headline, it's that the paper that that quote links to says there's no evidence for a recent population bottleneck.
Very interesting, I had no idea that Cheetahs had such an insane bottleneck. One question though, what do you mean by
"they are so genetically close that they can take each other"?
“Most demographers say we will hit 9 billion before we peak...”
I believe this thinking is very out of date at this point.
The 2017 UN Population Prospect report has the World population at 11.2 billion and still climbing by 2100. The population of Sub-Saharan Africa alone is projection to be over 4.1 billion which I have to imagine will be nothing short of a cataclysm if it actually gets to that. The data here is stunning:
The challenge with extrapolating is that you can't know what you don't know (for example in 1975 they didn't know about AIDs) and you can't know how a society will respond (like Japan going negative in population growth).
disaggregation is the key in everything. If 90% of the world decelerates at -1% a year but 10% accelerates at 10%, then for a few years it looks pretty close to flatline but the extrapolation of that is garbage. You have to have exact factor analysis.
Ahhh... The delicious taste of technically correct.
I actually find 11 gigahumans surprisingly low. Unbounded exponential growth would suggest something more like 30 or 40 billion. Clearly that can't go on forever, but exactly what effects are expected to dampen the current post-Industrial trend and why in the 21st century?
I highly recommend by the late Hans Rosling: Why the world population won’t exceed 11 billion. It explains quite well what the sister comment by riffraff refers to.
Wealthy people don't have many kids, as the average income goes up the number of kids per family goes down. Population has stopped growing in rich countries years ago, it is expected to happen in currently low income places too.
Access to better healthcare lowers the infant mortality rate. That than leads to couples having fewer children since they don't need to hedge their bets as much (ie having a more offspring expecting several to die). Combine that with easier access to contraceptives and you have some major reasons why birth rates decrease in developing countries which have the money to spend on healthcare.
In developed countries you may also have factors like people focussing on careers, valuing independence, more choice in relationships (i.e. divorce/separation being more acceptable) etc.
The biggest natural constraint was nitrogen fixation which places a natural limit of around 4 billion people. But artificial fertilizers basically took the lid of that and the population has been exploding since been the process was first industrialized.
Hmm, heard about the plummeting insect populations? Artificial pollination is possible but costly, the more we grow and adopt land solely for human populations; use pesticides to increase immediate crop yield; the more we remove natural ecosystems that currently act with our food production cycles.
The short answer is that there are no real physical constraints.
BUT there are some fairly important practical issues around unequal access to resources: some places have too much water and some don't have enough. Those kind of problems may lead to war, but probably won't stop population growth (short of it going large-scale nuclear or biological).
Population growth in many regions has already plateaued. At least the natural change. Europe, North America, Russia, China, Japan. The main outliers right now are India and Africa. But even those are expected to cool off after their initial burst. The true constraint is administrative capacity: will these countries be able to grow their infrastructure and improve their resource management before they turn their countries into deserts?
India will probably manage to, but some African countries probably won't. It's going to be quite bad for some unfortunate people living in these countries...
When countries packed with people grow resource scarce then the richer nations either share their resources, commit genocide by starvation, or go to war to keep the resources they have.
We can pack in more people but not if we hope to raise the living conditions of all those people. IMO those billions more are mainly going to be living hand-to-mouth in shanty towns. Whole countries living like that have little to lose by going to war to gain resources ...
While everyone is focusing on the bottlenecks and such that this might have caused in homo sapiens, the main thing for me is the relation between Toba catastrophe and the main human migration out of Africa, which came 60kya. My theory is that Toba killed off or severely weakened populations of other human species (Neanderthals primarily) that were claiming the areas in Middle East and thus blocking our expansion.
So instead of (or along with) having being a major threat for us, I think it's what enabled us to become the global species we are today.
The thing about the Toba catastrophe theory is that the best evidence for it is "there was a massive eruption ~73K years ago" (the largest in the past several hundred thousand years). Which is to say, there is no archaeological evidence of depopulation. I don't know the genetic evidence well enough, but Wikipedia's presentation of that evidence is non-sensical, and I don't think there is unambiguous genetic evidence that "humans were relatively inbred ~70kya."
Signs point to a long chain of great filters, as far as I can see:
- DNA/cellular Life itself: each is already highly improbable and hard to reproduce, and likely not even possible anymore in our current climate/atmosphere
- multicellular life is a lot more likely past step one, but still hard
- life that is maintainable and powerful enough to escape the struggle for survival long enough to bother with something like complex social structures and engineering (super unlikely because the more powerful you get, the easier it is for you to accidentally destroy all your food sources and starve to death until the system is balanced again)
My pet theory (completely unsubstantiated, of course) is that intelligent life is common but that it rarely develops money. Stuck with barter, most intelligent life never moves beyond low levels of trade and technology.
The concept of assigning value to largely useless objects and using them to keep score is extremely powerful, but also highly weird.
Have you read Debt: The First 5, 000 Years by David Graeber? While a lot of it is kind of... socialisty, it does a good job at describing how the standard "barter--> money" econ history is anthropologically wrong.
'Perhaps' this was the trigger for the end of other homo species and the location of certain group of Homo sapiens sapiens (modern humans) helped them survive the consequences of Toba?
Toba is possibly more fire and brimstone and hell on earth. Think about it, the sun would be blotted out, famine, war, destruction, ash everywhere. Its possibly the root source of our depictions of hell.
I think the flood is more likely to be related to our exit of the ice age and the resulting catastrophic flooding from the ice melt.
All speculative of course but its fun to speculate.
[1] https://en.wikipedia.org/wiki/Lake_Toba
[2] https://en.wikipedia.org/wiki/Medan
[3] https://en.wikipedia.org/wiki/Nias
[4] https://en.wikipedia.org/wiki/Angkor
[5] https://en.wikipedia.org/wiki/Srivijaya