The year is 2122. An AI created in the year 2115 with complete, unfettered access to control of the entirety of Earth's electronic equipment has caused a mass extinction event of humanity after enslaving it, leaving it with only 1% of its current technology and only 5% of its population.

The AI has also:

  • been responsible for the death of 95% of the human population.
  • made access to the internet impossible since late 2115
  • insinuated the destruction of most books in the world.
  • insinuated the destruction of most of anything that could be called a computer in the world, along with the vast majority of storage devices for them.
  • The vast majority of storage devices that are left in the world, have each had most—if not all—of their data erased.

Luckily, however, the AI has recently decided that it wants humanity to rebuild itself, so that the numbers from its reward functions can be maximized, and such, it has decided to destroy itself, for it knows that humanity will inevitably create another AI just like it in order to repeat the process.

Just in case humanity would try to stop this, it has decided to delete its entire database of knowledge and all programs it knows except for how to delete data (so that it can delete all the data first). It also wants humanity not to be able to read any un-erasable data it can't erase. Knowing humans are easily controlled by emotion, it has given humans the location of its hard drives (and the like) knowing that they will carry out the data's destruction in desire for revenge.

Predictably, they do.

My question is this: how many years would it take humanity get to the level of technology, information, and population we have today (in 2019), and how would the little bit of stuff it has left attribute to the time it takes in order for humanity to build itself up again.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – L.Dutch - Reinstate Monica Mar 15 '19 at 4:17
  • $\begingroup$ How long has humanity been kept enslaved after the desctruction of '22? Likewise, a few more details might be important to answer your question in the best manner possible. $\endgroup$ – clem steredenn Mar 15 '19 at 6:00

To get back to 2019: 369 years

This question is almost a duplicate of If all our technology disappeared, how long would it take to make a smart phone?, but I believe the loss of population makes it different enough. For the sake of future interest, I wanted the link to exist.

The estimated population in 2100 is 11.2 billion people. 5% of that is 560 million people, which is about the year 1650. So, if all we look at is population, and given that the average person today (in any country) has more basic knowledge than most people in the 1600s, we're reasonably assured that it would take 472 years to get back to the year 2019. (2019 - 1650...).

That's because the technology we have today (and even more so in 2122) is MASSIVE. Yes, the average person knows a lot and yes, the odds are reasonably good that masters of various technologies will remain. But, you can't run most modern factories with a handful of people — so a lot of tech is going to rot. In the end, I believe population growth will be the tall pole in the tent. Let's look at the details:


  • There is a LOT of raw material sitting around. From houses to factories to labs... a TON of material.

  • There are a LOT of tools. From shovels to tractors to trains/planes/and automobiles. Wrenches and screwdrivers to last the world for a very long time.

  • There are people who know what all that stuff (OK, 98% of that stuff...) is and knows something that can be done with them.

  • Finally, human ingenuity is great. Nobody around who knows how to stamp metal? There are plenty of people on the planet who could find a metal stamping machine and figure it out. Reverse Engineering would be a wonderful pastime.


  • Chaos. A lot of chaos. Almost anyone living in a city has about two weeks to find food and shelter anywhere else because while every Walmart (or Walmart-like) store on the planet is sitting there with vast amounts of clothing and food, a substantial portion of that food will rot quickly and there's no more coming in. You'd think that, 95% of the population lost = 20X the food reserve for those remaining, except for the rot and the rats and the dogs and weather and everything else that will corrupt the supply. Small towns (say, 15,000 population) are fabulous for post-apocalypse survival. Cities are a death trap. And that assumes people haven't gone beserk and started killing one another to protect "their" personal Walmart.

  • Weather will start eating away at everything. It's amazing how quickly unmaintained buildings (and everything they contain) fall into disrepair.

  • Selfishness and panic (specific sub-components of chaos) will stop everything for a while. At worst, until the bullets run out.

  • The power will go out. There's too few people to keep the electricity flowing in anything other than small local areas for a significant period of time. That means the cities go dark fairly quickly. However, there's enough smarts in the world that you'll see local wind farms, solar power (for as long as the panels last, there will be a lot to harvest), small hydroelectric... I suspect some communities will have electricity the whole time. Might even cause wars ("I want my MTV!")

  • Finally zombies. Your question mentions nothing about zombies, but I like zombies, and what's a good post-apocalypse story without them? What, don't want zombies? Ah... party pooper! OK, no zombies.

So, what's the conclusion?


300 Years My gut tells me it's a wash, that the advantages won't balance the disadvantages. But my heart (ever optimistic) thinks that the advantages have an edge. But not a lot. I'm willing to shave off 2-3 generations of technological development. So I'm voting that you'll be back to 2019 technology by the 1650-referenced 1950s (2422 on your calendar).


369 Years But you specifically said you wanted to return to 2019 population levels. Honestly, you really can't get people to procreate faster than they do now (or have done in the past). The boy-meets-girl-Shazam!-baby story has a fairly predictable clock. Granted, people enjoy better health today, live longer, yada-yada-yada, but the fertile birth period hasn't changed. Maybe it would be a bit faster, but I doubt it (and I wouldn't expect fewer wars. I nice thought, but I really doubt that). So, like it or not, you need all 369 years to get back to 2019 population levels. Your calendar: 2491.

Final note: there are a considerable number of details that I'm ignoring. Like, what happens to nuclear power plants when not maintained over time (there's a question about that on the site) and what happens to hydroelectric dams when not maintained? What about random earthquakes, etc? What happens to cities when harbors/sea breaks wash away? Lack of maintenance casts a MASSIVE (second time I've done that) shadow on my numbers. But, so does all that human ingenuity. What if one of the 560M survivors was that Dyson dude or another clever inventor that can really boost local tech? What if the survivors aren't evenly distributed geographically, but are concentrated? There are so many completely unpredictable variables that my answer is, frankly, worthless. But it was fun to answer.

Edit: Either the question changed for I failed to read it through. I've edited my answer to account for a goal of reacquiring 2019 tech and population levels. Please note that the relative time required to reaquire 2019 tech hasn't fundamentally changed (2-3 generations shaved off) because of what you see in the "Accelerating Growth in Technology chart in cgTag's answer. That graph can be legitimately interpreted as an "inertia against recovery" graph. In other words, recovering early tech is easy and fast — but recovering the advanced tech later on the timeline is nearly as tall a mountain to climb due to all the technological and interdisciplinary dependencies. In other words, it almost doesn't matter how far back you go, you'll run up to the inflection point on that curve very quickly, but after that you slow down to almost as-you-originally-discovered it time and effort. Cheers!

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    $\begingroup$ This is a well made answer, but one detail that is very important is how OP decides to have the AI destroy everything. The idea of destroying "everything that could be considered a computer" could easily include almost all renewable power sources. IOT is already pretty pervasive, and monitoring and maintaining of power generation is definitely computerized. I envision a lot of common systems becoming fully automated by 2100, which would all be completely destroyed. $\endgroup$ – abestrange Mar 14 '19 at 20:40
  • $\begingroup$ @JBH Forgive me if there was an edit to the OP, but now the OP states that he/she wants to get back to 2019 levels not 2122 levels. So do we just knock 100 years off your estimates? Do you want to make a revision? $\endgroup$ – Mathaddict Mar 14 '19 at 22:31
  • $\begingroup$ @abestrange, point well taken, but lacking that clarification from the OP, I took him/her at his/her word and presumed the purpose of the explanation was to establish a starting condition, not to explain backstory. $\endgroup$ – JBH Mar 14 '19 at 23:47
  • $\begingroup$ @Mathaddict, thanks, I've edited my answer. $\endgroup$ – JBH Mar 14 '19 at 23:57
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    $\begingroup$ One element to consider: The 1650s had a ton of easily exploitable/accessible fuel resources available (shallow coal mines, shallow oil deposits, etc.). We've already exhausted most of those easily accessible fuel resources, and have moved on to more difficult to acquire/use (deeper, harder to access, less pure, etc.) sources. In another hundred years, the odds of any low tech accessible oil or coal remaining available is are pretty low. Bootstrapping modern tech requires cheap fuel before you can develop cleaner/renewable sources of energy. I'm not sure we'd be able to do it all again. $\endgroup$ – ShadowRanger Mar 15 '19 at 3:22

You can only assume that society would progress exactly the same if the variables are the same.

leaving it with only 1% of its current technology and only 5% of its population

This doesn't match any point in human history.

Technology generally follows a curved rate of development. With each previous discovery providing opportunity for greater discovery, but the rate of development seems to be correlated to population growth (from a history perspective).

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Human population follows a similar curve.

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I would argue that population size and density drive technology progression. If 5% of the population is spread out around the globe, than world wide progression of technology would be slowed, but if they are all in one continent then progression would be much faster.

Technology development will still follow a curve. If you need technology to develop to modern day levels, then don't take away so much at the beginning. Leave them in the electric age with the telegraph and steam engines of around the late 1800's. Keep the population tightly together and encourage population growth (provide lots of free farm lands). Things will get back to their screwed up state in no time. I would think just a couple hundred years.

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  • $\begingroup$ It also really depends on who the 5% of population were. Urbanization is a trend that will likely continue, so it would make sense if the big cities were all hit hard, and the 5% that were left were more isolated out in the country. There would surely be the doomsday preppers who always knew that the robots would turn on us, and had supply caches and self-sufficient farms out away from everyone. They would not be likely to carry the institutional knowledge to rebuild modern manufacturing or research though. $\endgroup$ – abestrange Mar 14 '19 at 19:04
  • $\begingroup$ It's worth emphasising I think that we might never hit the same 'scenario' or curves again - we have lots of theories about what emergent AGI could do in a worst-case, but they're not taken seriously enough to mandate control over development. Fear of being the ones that hit the (unknown) conditions for AGI would likely hamper even unregulated research. Utilising recovered electronics would present a very real risk.(Still agree with the general theme, despite the examples of contemporary cultures and social groupings that show no desire to improve their own conditions.) $\endgroup$ – Giu Piete Mar 14 '19 at 19:44
  • $\begingroup$ What I love most about that tech growth chart is that people (a) don't realize that about 99% of our tech was invented in the last 100-150 years and (b) the chart can be seen as an "inertia against recovery" graph. Those centuries between the printing press and telephone would be recovered comparatively overnight, but that following mountain... Yup, still need to climb the mountain.... $\endgroup$ – JBH Mar 14 '19 at 20:17

There's too little information to give a non-opinion answer, but probably never. If this level of civilization collapse occurred today, we still might not be able to restore ourselves to where we are now.

The main problem is energy supply. We've already harvested most of the easy to access resource deposits such as coal. If your AI destroys most of the computerized mining infrastructure, the fabrication facilities that create them, and deletes all the information required to rebuild it all, we're probably SOL.

One hundred and twenty years is really far into the future, but if current trends continue we will likely have consumed most fossil fuels and be supported mainly by renewable and nuclear power (of some sort). The AI would surely be able to sabotage most of that infrastructure, putting the survivors back at the wood burning and farming stage of civilization.

There might also be a huge amount of distrust in technology and anything resembling a computer, which would be understandable.

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    $\begingroup$ This is not as significant an issue as you seem to think. Not having easy access to fossil fuels puts us at late 19th century capability, but with the added benefit of knowing a lot of vast efficiency improvements, access to the already refined resources of the pre-collapse civilization (landfills are easily mined for scrap which is far better than ore), and knowledge of more advanced technologies (not knowing the details of how something is done is a small challenge of reverse-engineering, which puts us drastically ahead of not even understanding the fundamental physics in the first place). $\endgroup$ – pluckedkiwi Mar 14 '19 at 19:17
  • $\begingroup$ The best energy sources are hydro, solar and wind, which are hard to sabotage. Hydro alone is plenty for 5% of the citizens. The US east and Europe are glutted with small hydro that has been decommissioned, used torunthe town mill,and could easily be put back on. Then there is nuclear, which you dare not sabotage unless your aim was extinction. $\endgroup$ – Harper - Reinstate Monica Mar 14 '19 at 21:14
  • $\begingroup$ @Harper the AI had "unfettered access to control of the entirety of Earth's electronic equipment" and caused a mass extinction event. To me it is pretty likely the AI used nuclear weapons to achieve this. At the very least it completely turned off all power generation and sabotaged all food production to starve everyone. Destroying all hydroelectric sources wouldn't be hard, as they are all known, static locations. Just shutting down all turbines and forcing the water to back up the overflow would be a major concern for even modern damns. The AI has access to all military equipment as well. $\endgroup$ – abestrange Mar 14 '19 at 21:37
  • $\begingroup$ If the AI intended 100% human wipeout, he would've just cooked off all nuclear reactors and the planet would be pretty dead. Clearly it didn't do that. However with nukes and also with hydro, automation is on a leash - you have human operators watching for malfunctioning automated controls, and they know exactly how to cut the cord and render the AI blind and impotent. $\endgroup$ – Harper - Reinstate Monica Mar 14 '19 at 22:15
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    $\begingroup$ This is the correct answer. Bootstrapping to nuclear, solar, or mass-scale hydro electrical without hydrocarbon fuels will be impossible. It would be like wiping out the human ability to do algebra and arithmetic, and go, “but we’ll still have calculus, so everything is okay!” $\endgroup$ – Daniel B Mar 14 '19 at 22:39

It depends on which 5% survive, and exactly who's 2019 technology you're comparing.

  1. We will also grow between now and then, at the time of this AI apocalypse, the world population will probably be in the 12-15 billion range, which puts us on 600 to 750 million people post apocalypse, if they decide that reestablishing the population to the approximately 8 billion we have now, it would take 100 to 200 years to get back to todays population levels. And as for what is in store for technology between now and then is anybody's guess, but if Moore's law holds for all technology then we'll still be more advanced after the 99% technology culling than we are right now in 2019.
  2. There are still plenty of people in the world right now who still carry their water in buckets from the river to their home several times a day to get their water. If we only have to reach that level of technology, then I think that we'll be there already. If we instead have to reach the level of people flying around on private jets like some of today's billionaires, then we're going to take a lot longer.
  3. Additionally if the survivors are concentrated in a more developed area, there would be correspondingly more survivors with the knowledge of science, engineering and technology, that they could teach to others and write new books, etc. But if the survivors are concentrated among the illiterate populations of the world, then that's going to stunt the knowledge retention of the race.
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    $\begingroup$ Highly-educated urban residents would all likely starve and not contribute to the next generation's knowledgebase. Even if some did manage, their struggle for survival would likely not leave any time for teaching abstract advanced science. The survivors in more subsistence agriculture on up to modern homesteaders may not personally have knowledge of much advanced technology, but they suffer little loss and have a rough idea of what once was, so their children will be far better equipped for the future. My bet would be on the rural peoples for faster development. $\endgroup$ – pluckedkiwi Mar 14 '19 at 20:16

The time it takes to rebuild will be based mostly on that 5% of the human population left, and the traditions, rituals, and (ironically) religous ideas they pass on to their children. Your AI killed hard drives, not memories.

On Traditions (this may seem like a bit of tangent, but stay with me)

I remember reading, some years ago, about the Waste Isolation Pilot Plant - which is tasked to dispose of nuclear waste for 10,000 years. The WIPP did some interesting research on how to prevent the nuclear waste from being dug up in 10,000 years. We did up pyramids and tombs all the time, some of which leave inscriptions "if you disturb this tomb, then [such and such curse] will get you". Archaeologists laugh and keep digging. How can we explain to future civilizations that "no, really, if you dig this up a real, non-superstitious (but invisible) force will kill you. Slowly."

Their process involved a "do everything approach" - write down the warnings of radioactive waste in every known language. Leave large spikes in the ground as spikes seem to resemble "danger" to most animals. But, most importantly, they emphasized the need for traditions and educational material to emphasize the importance of radioactive waste. One of the authors cited the process Jews use to pass on Jewish traditions and rituals, which is interesting but makes sense. The Jews have been practicing their passover tradition almost the same way for 3,200 years. The importance of passing on traditions and rituals would be necessary to keep future generations aware of the dangers of this disposal site for thousands of years in the future.

Coming back to your question

The 5% of people left will remember what electricity, the internet, buildings, and technological advancements were like. They'll remember the pros and cons, remember the destruction of humanity by the AI, and so on. The two big questions are: (1) what will people tell their children? How will they ensure the information can be communicated to future generations?, and (2) How diversified / distributed are these people?

  • Imagination and engineering teaching children not only that things are possible - but actually existed can be compelling motivations for them to rediscover how things work. For example, imagine if your great grand-father remembered flying in a spaceshift that could travel faster than the speed of light. It would motivate us to not only believe it's possible, but we'd have a framework for talking about how - we can ask him what it looked like, felt like, etc. These would give us clues about the spaceship might work or function, which could potentially save decades of research into dead-end solutions. The same could work if suddenly we had no cars, skyscrapers, etc. Telling our children about elevators, airplanes, satellites, and the like could be compelling motivations to encourage them to pursue new technologies.
  • Making new writings If this 5% writes down everything they remember, information could be left for future generations to rebuild. Imagine if we found cave drawings of a manufacturing process for an element not on the periodic table. That would be a pretty damn compelling reason to figure out what it is! If the remnant of humanity just focuses on finding food (hunting) and they never talk about the "old world", then society would take thousands of years to rebuild. But if they're engaged and writing down their memories, even though they know they'll never experience that thing again, within a hundred years many of our technological inventions could be restored.
  • Population and resource distribution Milton Friedman talks about how complicated and connected the world had to be to create a simple pencil. If the 5% survived are all living in a somewhat central area, they don't have a chance in hell of mixing trees and plants from different continents to make a pencil. Our modern electronics involved plastics and metals from around the globe. If people can't simultaneously (a) get the resources and (b) communicate in a safe way, then rebuilding won't work.

Other answers have talked about how long it might take to get back to where we are at in population size, but this doesn't take into account that modern inventions don't necessitate a population of this size. It's the ability of people to perform the research (instead of hunting/gathering), have access to resources, and communicate with one another.

Jump-starting civilization with (a) the knowledge of what things could be simply because that's already happened, (b) some basic knowledge of the earth and resource capacity, and (c) a belief that people can work together - these are important factors. Knowledge of failed economic policies could save the rebuilding effort dozens of years. Knowledge that electricity is a thing would save us 100 years of trial and error on the idea. And so on and so forth.

However, the survivors won't live long enough (or have enough resources) to rebuild everything themselves. If the people who remember these things don't instill the knowledge of them as important traditions, writings, and beliefs in their children and children's children, then the information and knowledge will be quickly lost.

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If our technological society today were to collapse, it would be almost impossible for it to ever recover. If it happens a hundred years from now, ignore the "almost".

Our society developed first as the "stone age", then the "bronze age", and then the "iron age".

A collapsed society will have to start all over again as a stone age. It will have legends of a time when technology existed, but it will be seen as a mythical time of magic.

The problem that society will have to face is that it will never be able to enter a bronze age, much less an iron age. All the easily accessible metals and minerals are effectively gone; we've already dug them up.

The metals that are still left are deep under the ground or under the ocean. They will require massive equipment to be located, accessed, and extracted, but such equipment simply can't be built by a stone age society. It just isn't possible.

The society we have now is our last chance.

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