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Starwulf
2015-11-06, 12:41 AM
So I just got done watching a movie where almost all of earths population was destroyed. Not sure how many were actually left, but the insinuation was "not many". So assuming there were about 5000 people left, and an even # of them were women(unlikely I know, but for the sake of this equation that's what I'm going with), how long would it take to reach a population of 100 million assuming that every woman was pushing out kids from the time they were capable(say 13) till the time they hit menopause and were no longer capable of giving birth(say 45)?

I'm no mathematician so I know my best guess is likely quite far off, but I'd have to think it would take at least 500 years, and probably much closer to a millennium. After that I imagine it wouldn't take nearly as long to get back to normal population levels, but to get to that point would certainly be rough. For the sake of the discussion also assume that every baby survives(though if you want to factor in an X factor for babies not surviving be my guest, I'm just trying to make it easier).

Eldan
2015-11-06, 05:44 AM
https://docs.google.com/spreadsheets/d/1IGbBBCkEU2ceNZrYP2hApTINlMtSAc8Mns29KKnPjqY/edit?usp=sharing

I've made a few assumptions:
Reproductive age is 15-45.
Age of death is 80, and there's no causes of death except old age.
Age distribution is originally perfectly even.

It's a bit weird for the first 100 or so years. Because of the perfect age distribution in the beginning, exactly 62.5 peope would grow up, enter menopause and die every year in the beginning. Then you'd have about 1000 babies a year, while still only 62 people die for the next many, many years, so you'd start with a population increase of 1/5, which is insane. It takes a long while for things to even out to "normal" exponential growth.

Anyway, unless I've made a mistake, you pass 100'000 in year 35, one million in year 60, ten million in 83 and 100 milion in 107.


This is very, very silly, of course. People don't work like that. Mostly, you'd have to include another factor for death rate across age ranges, not just an average death point where everyone dies. Plus child mortality. And no population would be able to feed that many babies and pregnant mothers.

factotum
2015-11-06, 07:31 AM
Not to mention not all women would be able to bear children, and others would simply not agree to being turned into baby-making machines, even when the good of the entire species is at stake...

Eldan
2015-11-06, 07:58 AM
Yup. Under this model, every single woman has 30 children in her lifetime. Good luck convincing anyone to do that. Or finding a way to raise them.

The growth rate in my model starts at 17.8% per year, steadily goes down to 4.6% per year by year and then rapidly increases again to 10% per year. From then on, it stays between 9 and 11% per year.

Modern human society worldwide has 1.1% per year. Just to give you an idea.

Eldan
2015-11-06, 08:04 AM
Another statistic for this:

at the start, 19% of the population are under 15. By year 5, half the population is under 15. By year 27, over 70%. Most of the time, it's over 76%. That means 3 out of every 4 people are children or teenagers.

thorgrim29
2015-11-06, 09:56 AM
Also if there's only 5000 people left on earth unless they're all in one town to begin with most of them will probably never know they're not the last survivor.

Eldan
2015-11-06, 10:24 AM
Well, yes. We also need assortative mating.

Ravens_cry
2015-11-06, 02:45 PM
Preindustrial, subsistence level agriculture/hunter gatherer based society is going to mean a LOT of infant mortality, and it's going to mean a lot of otherwise preventable adult deaths as well. Sure, it makes the math easier, but it skews the actual numbers so bad as to be useless even as a rough estimate.

SirKazum
2015-11-06, 02:57 PM
Rather than pure maths, I like to think about this sort of scenario (yes I think a lot about post-apocalyptic repopulation... what? :smalltongue:) in terms of comparing it to the population of the smallest, self-sufficient settlements.

Towns can get pretty small, like maybe a few dozen people, but they start having trouble sustaining any sort of complex civilization without outside help, and quite often die out as well (if there's a disease outbreak, poor harvest leading to starvation, or some other crisis). Besides, inbreeding is a very serious problem in such tiny population, at least without a steady migratory flow. Towns with populations in the tens or hundreds seem to not grow much over time... though I don't know how much of that is due to people just leaving that godsforsaken podunk place.

Populations in the low thousands seem to be healthier as far as maintaining a self-sustaining, isolated society goes... I've read somewhere that the minimum number of individuals in a given species to ensure healthy, long-term survival of the species is 2000-something. No idea why that is, but it probably takes into account inbreeding (or prevention thereof), being capable of enduring crises and periods of populational stress, and other such long-term viability concerns. As far as a human population goes, 2000 people seem capable of maintaining a functional society with a reasonable level of modern amenities.

Of course, that's not what you're asking... you're asking how long would they take to bounce back to a significant number of people. Firstly, what I'm saying is, if you can get all 5000 of those people in the same place and reasonably working together, long-term survival of humankind isn't that serious of a concern. Barring further catastrophes, we'd make it. But as for regaining population... I think it depends a lot more on available resources. Raising kids ain't easy. Your population's demographics (age and gender distribution mostly) would also mean a lot. But, if circumstances are favorable... remember the world population more than tripled in the last century, and that's just "normal" populational growth (i.e. people weren't deliberately trying to breed like bunnies and moving into available, unused space and resources). The increase per century in your scenario would probably be even greater. And such multiplicative growth really adds up over time. If population increases 5x per century, you're looking at 25,000 after 100 years, 125,000 in 200 years, 625,000 in 300 years, 3,125,000 in 400 years, and 15,625,000 in 500 years. The 100-million mark would be hit sometime between 600 and 700 years. That is, of course, an extremely gross simplification based on a wild guess at a 5x per century growth rate. I bet the actual growth rate could be much faster than that, at least for limited periods.

Ravens_cry
2015-11-06, 03:14 PM
According certain theories (https://en.wikipedia.org/wiki/Toba_catastrophe_theory), humanity itself fell to around these levels at some point, and, as should be obvious, we have indeed, 'bounced back', though we have less genetic diversity than a single chimpanzee troop.

Kato
2015-11-06, 06:06 PM
Well, so I wanted to write a very basic simulation for the problem giving me the chance to change some things like birth rates to see how e.g. a woman giving birth about five times in her life instead of every year would affect the problem... Sadly I'm apparently so not used to most basic programing anymore I can't get octave to do what I want :smallfurious:

Anyway, obviously a lot depends on what kind of society/technology you have left. Given a certain basis and a wide enough array of skills and deciation, I guess 5000 people could be enough to keep things running normal-ish for the small population, considering they start out by salvaging ressources instead of tying to get everything on their own to start out. Assuming more normal birth rates than Eldan I guess it would take a while longer, I think something like log(1/birth rate)*100? No, that doesn't make quite sense... I wish these few lines of code wouldn't anny me so :smalltongue:

Starwulf
2015-11-06, 08:51 PM
This is definitely some interesting stuff here all, I really appreciate the responses :) Kind of crazy to think that if there were zero deaths in the women breeding or the kids being bred that we could reach 100mil by 107 years. Virtually impossible for something like that to happen of course, but nifty nonetheless ^^.

Thanks for the link to that Toba catastrophe, I always like to read about stuff like that!

Eldan
2015-11-07, 04:11 PM
No child or childbed mortality is one problem. One just as big probably is that every adult has to be able to constantly watch and feed three children on average. Or probably more, in the case of the men and the old, since the women are also constantly pregnant and probably can't work as much.

McStabbington
2015-11-07, 08:01 PM
There's also the fact that without any further information about what exactly dropped the population in the first place, it's difficult to get a bead on exactly what the age distribution for the remaining population is. Most diseases hit the very young and very old with particular virulence, which concentrates the remainder in the breeding age bracket.

A war, by contrast, has the effect of carving holes in breeding age demographic brackets, at least among males. There were instances in particularly brutal conflicts like the American Civil War, World War 1, or the Soviet theater of World War 2 where every male of breeding age in an entire town died; males within a 30-year age bracket simply ceased to exist.

If you assume normal population distribution, then some of that 5000 will have passed breeding age or be too young. And you have to factor in that even with artificial insemination, fertilization rates for any one ovulation window are usually pretty low. Our rates of population growth have more to do with there being lots of women of childbearing age bonking than any actual biological explanation for our amazing fecundity.

Long story short, if our numbers dropped to 5,000, I'd expect our rate of population growth to closely mirror the growth our species has already displayed: it would take thousands of years to get to 100 million, then a few hundred to get to 1 billion, then a few decades to get to 2, etc. It's a geometric ratio with a fairly high exponent until the population starts reindustrializing.

BananaPhone
2015-11-08, 02:53 AM
You could just go for a population growth percentage per year. But there'll also be the question of "what are the women doing?" If most of the women are helping in the work-force with re-building society then they might not have the time/focus/energy to be having lots of children - but that might rebuild social infrastructure quicker. But if they become united on the idea that getting the human numbers back up is #1 priority, and dedicated themselves to child-rearing, then the population might grow a lot quicker (but this approach could have social ramifications for when things become more "normal" and the need for population growth isn't as expedient).

This isn't set in stone of course. It's entirely possible for each fertile woman to have a couple of kids while contributing to society in other ways, much the way as women balance careers/children in today's society. But if Western birth rates are any indication, this will keep things relatively stable rather than deliver the explosive growth required for 100,000,000 citizens asap.

But then there'll be other compounding factors such as long-term access to food, infant mortality rate, childbirth mortality rate, fertility rates, access to medicine and childbirthing facilities etc lots of things to consider.

Probably the simple way to go would just be to assume a population growth percentage per year of something like 1.2%. I'm pulling that figure completely out of the air, but it's similar to the world growth rate at large.

We take that number over to this site: http://www.metamorphosisalpha.com/ias/population.php

I'm not 100% sure as it's been a few years since I was in a Statistics classroom, but I think it uses a similar formula to calculating money growth over time via compound interest.

And it'd take about 830 years for 5000 people to grow into 100 million. That's assuming 1.2% is the average over that time. There could be another extinction event, or a baby boom period.

Take what I say with a massive grain of salt, however, as like I said it's been a while since I've been in the statistics classroom so I could be massively way off :smallwink:.

sktarq
2015-11-08, 11:01 AM
Also you run into issues of effective childrearing and just how fast most couples breed in a preindustrial system.
In a settled usually agricultural setting it is about every other year. Non settled (hunter-gathers usually). About every 3-4 assuming previous child survived.

Also remember that even many modern societies have easily doubled in two/three decades when various limits on growth have been removed-I would expect similar behavior in the repopulation after such a catastrophe as long as it is an ark type scenario instead of a dusting of scattered survivors.

veti
2015-11-08, 03:24 PM
Preindustrial, subsistence level agriculture/hunter gatherer based society is going to mean a LOT of infant mortality, and it's going to mean a lot of otherwise preventable adult deaths as well. Sure, it makes the math easier, but it skews the actual numbers so bad as to be useless even as a rough estimate.

Well, we wouldn't necessarily be bounced right back to that level. We could assume (1) the whole 5000 of us are living in one community, (2) it's on nice fertile ground with no major predators or health hazards (I'm thinking maybe the south of France), (3) the survivors include at least a couple of doctors, a couple of engineers, builders, pharmacists, a couple of dozen farmers, and some means - let's not dwell too much on exactly how - for them all to pass their expertise on to others. In that case, we (I'm assuming I'm one of the survivors, otherwise it's not much fun) would be a lot better off than any pre-industrial hunter-gatherer society.

Let's assume kids are big and strong enough to start work at the age of 11, and people over the age of 60 are too weak to continue with hard physical labour, but they can still contribute as educators, childminders and so on. Women of childbearing age are excluded from the workforce, because bearing (and helping to raise) one child a year sounds like a 24/7 job to me. That gives an initial labouring-age population of (5/8 * 5000 =) 3125, less 938 childbearing women = 2187 potential labourers, to feed a population of 5000 - that's easy, you don't even need professional farmers to make those numbers work. After 10 years, the same number is feeding a population of 13,755 - still completely doable, with our rosy assumptions. And things only get better from then on, as new people enter the workforce.

It'd be a buttload of work. The politics would be scary, and I haven't really touched on the education of all these kids. But in terms of raw physical capability? - I think it's possible.

noparlpf
2015-11-08, 04:23 PM
With such a messed up, dystopian model, we may as well maximise the use of resources by doing away with 95% of male infants. Keeping them alive is basically a gambler's fallacy. Sure, you've wasted ten months of resources on the pregnancy, but the majority of male children don't contribute anything to the maximisation of population growth, they just drain resources that could go towards nourishing breeding females.

BananaPhone
2015-11-08, 06:51 PM
But now you've shed an entire generation of young men that are invaluable for working, particularly in rebuilding infrastructure and growing food as two essentials. You've also now cut in half your potential pool of innovative talent for both science and engineering. This isn't even going into the potentially disastrous social ramifications of a couple of generations being so overwhelmingly dominated by one gender (all of whom are expected to "breed" with men much older than themselves, which in itself could create a genetic bottleneck).

Crow
2015-11-08, 07:56 PM
I don't think this is a question for mathematics, but for sociologists. There are far too many factors to take into account for a question like this to be answered mathematically. Your best best is to look at past and present examples of population growth and birth rates and make an estimate from there. The highest birthrates in the world are currently in parts of Africa, with each family producing about 5 1/2 offspring. Many of those live in conditions that could be comparable to a society reset. That doesn't take into account how many of those die however.

Some of the measures being proposed in this thread would lead to massive war and upheaval, not to mention massive food shortages, which are going to decrease your production significantly.

noparlpf
2015-11-08, 08:15 PM
But now you've shed an entire generation of young men that are invaluable for working, particularly in rebuilding infrastructure and growing food as two essentials. You've also now cut in half your potential pool of innovative talent for both science and engineering. This isn't even going into the potentially disastrous social ramifications of a couple of generations being so overwhelmingly dominated by one gender (all of whom are expected to "breed" with men much older than themselves, which in itself could create a genetic bottleneck).

Ew, no. The old men can die off.

You keep enough new males alive per generation to maintain genetic diversity. Adults breed more successfully than early-pubescent teens, so you use the teenage females (and the small male breeding population) as a workforce and don't start breeding females until they're twenty or so. At that point they'll have more time to sit around because it's hard to do physical work after the first couple of months of pregnancy, so they can get the advanced educations and work on science and engineering.

Humans aren't really a great species for rapid population growth due to the small litter size, long gestation time, and greater-than-normal incapacitation during the latter half of pregnancy. So you need to rethink your entire model to maximise resource utility. Males are only marginally more useful than females for physical labor—see the number of farming civilisations in which the women did most of the farm work. Males are no better than females for academia or innovation. Therefore, maintaining as many males as females is a waste of resources.

BananaPhone
2015-11-08, 10:29 PM
What you're describing sounds rather...nightmarish to me.

I'm going to return to and stand by my prior point of just using a simple growth percentage (like 1.2%) per annum and use it to calculate population growth over X years, in much the same way that one can calculate the growth of money over time with compound interest.

All these problems people are bringing up are solved/navigated by countries today and throughout time, yet 1.2% growth rate remains about average.

sktarq
2015-11-08, 11:36 PM
1.2% is really low for a low pressure situation. Hell from the 60s-'70s Bangladesh was running in the mid/high 2.% range -basically 2.5% would be a more reasonable guess.

BananaPhone
2015-11-08, 11:40 PM
From what I understand 1.2% is the average for the world as of the past century.

Draconi Redfir
2015-11-09, 01:52 AM
Not to mention not all women would be able to bear children, and others would simply not agree to being turned into baby-making machines, even when the good of the entire species is at stake...

It's a thought expariment, you don't really need to take individual considerations like that into account. Everyone is fully aware that this would likely be the cas,e but for the sake of the expariment and to determine an acceptable average, you must act as if it were true.

veti
2015-11-09, 02:12 AM
From what I understand 1.2% is the average for the world as of the past century.

Yes, but that's quite a crowded world. In many countries, governments have been actively trying - by law or policy or education, or all three - to keep birth rates down. In this hypothetical, it seems safe to assume that policies would be directed the other way.

An empty world means, effectively, unlimited resources. People would breed like billy-oh in that situation.

Crow
2015-11-09, 03:02 AM
Traditionally, abundance of resources does not increase birthrates. What it does is reduce infant mortality. If anything, birthrates lower during long periods of sustained abundance.

The highest birthrates in the world are in N i g e r, at 51.26 per 1000 people.

Ravens_cry
2015-11-09, 03:53 AM
Well, we wouldn't necessarily be bounced right back to that level. We could assume (1) the whole 5000 of us are living in one community, (2) it's on nice fertile ground with no major predators or health hazards (I'm thinking maybe the south of France), (3) the survivors include at least a couple of doctors, a couple of engineers, builders, pharmacists, a couple of dozen farmers, and some means - let's not dwell too much on exactly how - for them all to pass their expertise on to others. In that case, we (I'm assuming I'm one of the survivors, otherwise it's not much fun) would be a lot better off than any pre-industrial hunter-gatherer society.

Let's assume kids are big and strong enough to start work at the age of 11, and people over the age of 60 are too weak to continue with hard physical labour, but they can still contribute as educators, childminders and so on. Women of childbearing age are excluded from the workforce, because bearing (and helping to raise) one child a year sounds like a 24/7 job to me. That gives an initial labouring-age population of (5/8 * 5000 =) 3125, less 938 childbearing women = 2187 potential labourers, to feed a population of 5000 - that's easy, you don't even need professional farmers to make those numbers work. After 10 years, the same number is feeding a population of 13,755 - still completely doable, with our rosy assumptions. And things only get better from then on, as new people enter the workforce.

It'd be a buttload of work. The politics would be scary, and I haven't really touched on the education of all these kids. But in terms of raw physical capability? - I think it's possible.
Education will help, yes, but, in practical terms, what good is it going to do? Sure, a doctor knows how to use medicine, but they certainly don't know how to make antibiotics, anaesthetics, and other medicines from scratch, let alone the tools of the trade. Sure, they can scavenge some things, but that won't last a generation.
Same with your engineers. Modern society is a web, and even a concentrated fragment of humanity is going to have to deal with the fact that there isn't the rest of the world to make the things you need to make the things you need.
Also, your numbers are way off. The Middle Ages, which actually had some significant innovations in agriculture, like the padded horse collar (getting better use out of the faster horse) and more advanced crop rotation, had a ratio of farmers to non-farmers of 4:1. I don't see how you can get something closer to half farmers and half not.

sktarq
2015-11-09, 09:45 AM
From what I understand 1.2% is the average for the world as of the past century.

While that may be true for the world as a whole (I didn't double check it) this situation would have more in common with places like Bangladesh, Nigeria, and the African Lake District than China (with its one child policy), Italy, or Japan.

As for the abundance growth link it is skewed by the link between education/development (which is a factor that lowers birth rates) and resource availability (which drives birth rates up). If you just give more space and an agrarian economy (which is what a 5000 population community would be limited to) then it expands quickly (see areas that gain new crops, medical abilities, or even just boarder stability that allows for development of former "buffer" regions.

veti
2015-11-09, 03:46 PM
Education will help, yes, but, in practical terms, what good is it going to do? Sure, a doctor knows how to use medicine, but they certainly don't know how to make antibiotics, anaesthetics, and other medicines from scratch, let alone the tools of the trade. Sure, they can scavenge some things, but that won't last a generation.

That's why I mentioned pharmacists. Doctors may not know how to synthesise drugs from first principles, but pharmacists should have a good idea of how to create a wide variety of medicinally effective compounds from just what they can grow in their own gardens.


Same with your engineers. Modern society is a web, and even a concentrated fragment of humanity is going to have to deal with the fact that there isn't the rest of the world to make the things you need to make the things you need.

And the same goes for engineers. Of course they won't be creating ASICs and nanobots anytime soon, but a well trained engineer will be able to work out, quickly, very efficient ways to dig wells, irrigate fields, treat sewage, insulate homes, and lots of other extremely applicable tasks. At the university I went to, you could specialise your whole engineering degree in "Appropriate Technology", which meant "the kind you could do in a village in the middle of Congo where they'd never so much as heard of electricity." And even those of us who didn't take that specialisation - we still learned things about metallurgy and the shape of gears and the design of structures that would make a medieval craftsman gape, even without particularly advanced equipment.


Also, your numbers are way off. The Middle Ages, which actually had some significant innovations in agriculture, like the padded horse collar (getting better use out of the faster horse) and more advanced crop rotation, had a ratio of farmers to non-farmers of 4:1. I don't see how you can get something closer to half farmers and half not.

Yes, the middle ages had plenty of innovations, but we don't have to rediscover those - we already know them, and better, at least in principle. We should be able to do significantly better than that. And in the scenario as described, we have several inbuilt advantages: we start with a good position, we don't have to spend resources on defence, our medical knowledge is vastly better, our political and social systems are hugely better. And engineering.

factotum
2015-11-09, 05:52 PM
but pharmacists should have a good idea of how to create a wide variety of medicinally effective compounds from just what they can grow in their own gardens.


I don't think it necessarily follows. A pharmacist may well know how to combine a bunch of chemicals in the lab into medicines and the like, but actually extracting those chemicals in the first place may well not be their speciality, and even if it is, they're likely to be trained in industrial-scale machine methods of said extraction, not boiling things up in a kettle on the counter! My training is in electrical and electronic engineering, but that doesn't mean I could build you a turbogenerator or figure out a way to create light bulbs when the scavenging supplies of those have dried out.

BananaPhone
2015-11-09, 07:05 PM
While that may be true for the world as a whole (I didn't double check it) this situation would have more in common with places like Bangladesh, Nigeria, and the African Lake District than China (with its one child policy), Italy, or Japan.



Yes, but that's quite a crowded world. In many countries, governments have been actively trying - by law or policy or education, or all three - to keep birth rates down. In this hypothetical, it seems safe to assume that policies would be directed the other way.




You guys are absolutely correct that growth differs from country to country and even from decade to decade. But given that we are talking about 5000 becoming 100,000,000, it'll take centuries at least - a lot can happen in that time. Some decades/years it might be higher, other times it might be lower, thus why I think it's safer to use the worlds average for the entirety of the time.

noparlpf
2015-11-09, 07:45 PM
I don't think it necessarily follows. A pharmacist may well know how to combine a bunch of chemicals in the lab into medicines and the like, but actually extracting those chemicals in the first place may well not be their speciality, and even if it is, they're likely to be trained in industrial-scale machine methods of said extraction, not boiling things up in a kettle on the counter! My training is in electrical and electronic engineering, but that doesn't mean I could build you a turbogenerator or figure out a way to create light bulbs when the scavenging supplies of those have dried out.

Yeah...I could get you some very basic meds, like low-dose aspirin from willow bark, but I have no idea how you go from the middle of the woods somewhere to producing literally anything we use on a daily basis at work. I guess depending on the nature of the apocalyptic setting there might be textbooks or manuals available on college campuses, but you're still going to need to get some of that fancy lab tech up and running to make a lot of things properly.

Icewraith
2015-11-09, 08:02 PM
For reference, four generations ago in the American Midwest, I have a relative-in-law who birthed... it's either thirteen or seventeen children (several of which did not make it past 12) and an additional either four or six stillborn. One woman, with (presumably) one man. (She died at some point and IIRC the guy went on to have six more kids with someone else.) Agricultural practice in a lower tech environment doesn't just mean growing your own food, you also grow your own labor. Women in poor conditions simply can't afford to JUST be pregnant full-time, and even if your mobility is impaired, regardless of whether it's from an eight months pregnant belly or an injured limb, you can still do useful things with your hands like cook, perform useful crafts (pottery, fabrics, edged stone weapons or tools), take care of injured or sick people, and teach the children (not just yours) how to do all of that. You can't hunt (as well) but you can still gather ripe fruit or domesticate animals. Once you get past about three or four sequential kids, the older ones learn how to take care of the younger ones on top of carrying water and performing decreasingly minor tasks as they age.

Population scaling doesn't work well in a hunter-gatherer society full of isolated villages, but it does work if agriculture as it existed 130+ years ago, or even 80 years ago is possible, simply because once you can produce enough food to sell to other people you by definition can support a larger family and sell less to other people.

So, depending on the conditions, if agriculture and anything usable as a draft animal (not even anything with a motor, just cows or horses) is still around, you can somewhat reliably get 4-8 kids that survive to reproduce from two parents. The first generation or two might be rough depending on what has survived and what has not, but once you get past that the survivors will have optimized for the environment and resources available and will begin reproducing at whatever growth factor is capped by local resources. 5x might be pushing it, but 2-4X population growth is not unreasonable.

Coidzor
2015-11-09, 08:25 PM
With such a messed up, dystopian model, we may as well maximise the use of resources by doing away with 95% of male infants. Keeping them alive is basically a gambler's fallacy. Sure, you've wasted ten months of resources on the pregnancy, but the majority of male children don't contribute anything to the maximisation of population growth, they just drain resources that could go towards nourishing breeding females.

No, farmers and laborers produce the labor and food necessary to maintain a population of women who are reproducing. Even assuming that somehow modern people from industrialized societies are able to go back to the point of working as hard as even their grandparents or great-grandparents, the ability of most women to provide useful labor in a suddenly pre-industrial society is greatly reduced for a quarter of a year to half a year.

Which is great if you time it so that they're of reduced efficacy for the part of the growing season that largely amounts to waiting around with ones' thumbs up ones' arses. Not so great if you find that humans don't always get pregnant on a nice timely schedule, especially if you stretch your stores of semen thin across multiple women at a time or go through each woman in sequence until they're pregnant.


Yes, the middle ages had plenty of innovations, but we don't have to rediscover those - we already know them, and better, at least in principle. We should be able to do significantly better than that. And in the scenario as described, we have several inbuilt advantages: we start with a good position, we don't have to spend resources on defence, our medical knowledge is vastly better, our political and social systems are hugely better. And engineering.

The question becomes, how low will your society end up teching down before it is at a level of agricultural and industrial capacity that is sustainable in the long term for the new society.

nedz
2015-11-10, 05:06 PM
Yup. Under this model, every single woman has 30 children in her lifetime. Good luck convincing anyone to do that.

More than 30 is possible (https://en.wikipedia.org/wiki/List_of_people_with_the_most_children), it's just not very likely.

Starwulf
2015-11-11, 02:28 AM
Hi all, I'm back! After reading through all the comments(again, highly interesting stuff to me, and a lot of you have made it quite understandable for me, which is great), I wanted to throw a small wrench into the scenarios. The movie I watched had access, and knowledge of fairly advanced technology, like a fair amount further ahead of us. Not sure how much that would affect things, but figured I'd throw it into the equation :)

Coidzor
2015-11-11, 04:01 AM
Hi all, I'm back! After reading through all the comments(again, highly interesting stuff to me, and a lot of you have made it quite understandable for me, which is great), I wanted to throw a small wrench into the scenarios. The movie I watched had access, and knowledge of fairly advanced technology, like a fair amount further ahead of us. Not sure how much that would affect things, but figured I'd throw it into the equation :)

Ultimately it boils down to how sustainable that tech level was. If they could make it last until the next two or three or however many generations were able to help maintain things and prevent having to tech down, then they're sitting pretty.

If they have to tech down to a level that's more sustainable until they get enough people to maintain the infrastructure necessary to tech back up, then it gets complicated.

factotum
2015-11-11, 07:16 AM
If they could make it last until the next two or three or however many generations were able to help maintain things and prevent having to tech down, then they're sitting pretty.


Which does rather require that some of the survivors are familiar with the repair and maintenance of said tech, and the likelihood of that could well be quite low when you only have 5000 survivors from a population of billions. For example, if this happened on present-day Earth, how likely is it that even one of the survivors would be a power station technician or engineer? If you don't have one of those you don't have electricity, and all the high-falutin' tech in the world won't help you if you have no means of powering it.

Rockphed
2015-11-15, 09:23 PM
No child or childbed mortality is one problem. One just as big probably is that every adult has to be able to constantly watch and feed three children on average. Or probably more, in the case of the men and the old, since the women are also constantly pregnant and probably can't work as much.

My parents had 5 children within 5 years, and their pregnancies were super-weirdly close together. Somehow the two of them managed to have 2 more kids and raise all of them to adulthood. They know some people who had 17 children, and raised about 15 to adulthood. I think 1 kid per year for 30 years is undoable, but 1 every other on average is. 15 kids per woman was not unheard of before the 20th century, though it was often tied to only 1 or 2 living to adulthood. Or 15 living to adulthood in a freak "everything went horribly right" kind of way.


Which does rather require that some of the survivors are familiar with the repair and maintenance of said tech, and the likelihood of that could well be quite low when you only have 5000 survivors from a population of billions. For example, if this happened on present-day Earth, how likely is it that even one of the survivors would be a power station technician or engineer? If you don't have one of those you don't have electricity, and all the high-falutin' tech in the world won't help you if you have no means of powering it.

So, if you were building a colony to survive the end, who would you pick? What books would you stockpile? What resources? How many people would you invite?

On the other hand, how far would you be willing to tech down? 120 years ago, all work was done by hand, by animals, or by steam engines, and steam engines were only used for large machines. Okay, so technically people used wind and water power, but those are largely location dependent. If you are willing to tech down to draft animals, you might be able to bounce back very quickly. If you keep good textbooks, you can probably bounce back as soon as your population is large enough, a la "Canticle for Leibowitz".

McStabbington
2015-11-15, 10:39 PM
Teching down to roughly steam engine tech should be pretty sustainable. Anything else likely not, if for no other reason than because there's a lot of modern conveniences that are based on natural resources that are by no means close to one another. The single best place to find nitrates for fertilizer is in Chile. The place to go for crude oil is the Middle East, while shale oil is in Canada. Steam engines are low-efficiency, but so long as you can get wood, you can run them, and wood is everywhere. Higher efficiency technology depends on having specialized workers to mine, refine and ship certain products. 5000 people just won't allow for that level of specialization even if the distances weren't prohibitive.

factotum
2015-11-16, 03:19 AM
So, if you were building a colony to survive the end, who would you pick? What books would you stockpile? What resources? How many people would you invite?


I got the impression from the OP that the 5000 survivors would be largely random, and that's the assumption I went with when I made my comment. Sure, if you can hand-pick the appropriate 5000 people and corral them into a specially built facility then surviving the end without losing tech is a far more reasonable proposition, but I didn't think that's what we were discussing.

Icewraith
2015-11-16, 03:51 PM
I got the impression from the OP that the 5000 survivors would be largely random, and that's the assumption I went with when I made my comment. Sure, if you can hand-pick the appropriate 5000 people and corral them into a specially built facility then surviving the end without losing tech is a far more reasonable proposition, but I didn't think that's what we were discussing.

Well, it's also how badly damaged is the infrastructure, what resources are available.

For instance, if the 5000 people are more-or-less randomly distributed over the earth's land masses, all the tech is gone, most large animals suitable for draft work have died out, and the forces that caused the mass die off are still in play, it doesn't look good for our survivors.

If the 5000 people survive because they lived in small isolated communities that weren't targeted by something like biological weapons, and the bio weapons' effects have mostly died out or are confined to recognizable and avoidable areas, and there is a similarly sustainable population of cattle, dogs, and edible plants available, odds for survival are much better.

Add in that in a mostly instantaneous event like a mass nuking or sudden non-recurring plague, the distribution of survivors might be strongly favoring two types of people- those whose professions depend on having a boat, or those who are wealthy and/or educated enough to own one and happen to be in the middle of the ocean when the disaster strikes. On one hand, you might end up with a non-viable population of rich retirees. On the other hand, you might have a boat with 200+ extremely fertile college educated kids out for a booze cruise (plus staff, especially chefs), a couple fishing boats full of men with practical survival knowledge (ropes, fishing, engine and electrical repair), and one solar-powered pleasure yacht with ten (possibly old) rich smart guys, the twenty hottest women on the planet (from various cultures), and a laptop that happens to have a selection of major science and engineering texts in its onboard memory.