The tech tree of reality

[Bohandas]

Some of the discussion in the thread about using time travel to accelerate progress got me thinking about how many technologies are dependent on previous technologies, and those technologies are depemdent on older technologies still

So, do you know if anybody anywhere ever compiled a detailed list of all the steps it would take to build a modern civilization from the ground up, completely from scratch, starting with no tools?

And if not, what would it take to compile such a list?

[Anymage]

This comes to mind as an admittedly entertainment-based source.

In-depth knowledge tends to be long and dry, however. Even if you just wanted to outline from the stone age to near-modernity, a full guide would be too long and cumbersome for anyone to meaningfully read or follow. However, a lot of the boring nitty-gritty details are required to make things work. So the essential skills training to survive if you wound up trapped in the preindustrial past would be a very different set of training than a broad outline of what tech/science would turn out useful.

[Bohandas]

To be honest, even though It was the time travel thread that got me thinking about it again, I'm more interested in if you got trapped on an uncharted island and wanted to do more than merely survive like some caveman. Or if the world's infrastructure was destroyed by some kind of global disaster, how would we miminize the duration of the service interruption in order to prevent society from being plunged into a barbaric pre-industrial state and toxic elements of society taking over.

Although the back in time angle remains of interest too. The hope is that if everything were laid out clearly enough and efficiently enough we might be able to speedrun history fast enough to bypass the formation of social mores and other cultural elements based on those earlier stages of developmemt, and that would prevent them from holding us back now

EDIT:
Also IIRC I actually bought that book based on a similar suggestion from an earlier discussion of this nature, but I never bothered reading it because it quickly became apparent that it didn;t fit the bill even a little bit (except for the title)

[halfeye]

This was more or less the concept behind the british TV show Connections:

https://en.wikipedia.org/wiki/Connec...h_documentary)

Obviously it probably had gaps, but the idea was there. There was a book, I don't know whether it's still in print.

[Smoutwortel]

Some of the discussion in the thread about using time travel to accelerate progress got me thinking about how many technologies are dependent on previous technologies, and those technologies are depemdent on older technologies still

So, do you know if anybody anywhere ever compiled a detailed list of all the steps it would take to build a modern civilization from the ground up, completely from scratch, starting with no tools?

And if not, what would it take to compile such a list?

It would take a deep understanding of history, ciivilization, sociology and technology.
The list would be severely shorter though than the path we took, because a lot of steps can technically be skipped without issue.
For example complex long distance communication technically only requires an effective medium, which can be acquired with rope and scripture can be decided in a gathering instead of letting it grow organically.

[Storm_Of_Snow]

It would take a deep understanding of history, ciivilization, sociology and technology.
The list would be severely shorter though than the path we took, because a lot of steps can technically be skipped without issue.

Not really, for example, you can't build a blast furnace for processing iron ore without some form of tools to dig the raw materials out to make the refractory bricks, the fuel to actually heat it up (whether that's coal, wood/charcoal or natural gas if you can contain it somehow) and the iron ore itself. And then you've got to transport all of them from where they're found to your production site.

And then there's the other technologies you also need - a sewer system, clean water and medical care to stop people dying, paper and printing so you can educate your work force, agriculture to keep them fed and so on, and those technologies also rely on the technologies you're working on (iron for your printing press and plough for example).

Of course, you can potentially shorten how long you need to rely on some of the technologies - you only need bronze tools until you can make iron in sufficient quantities and those iron tools can themselves be replaced with steel at some point, while a horse/ox drawn cart carrying materials weighing in the 10's to 100's of pounds for a few miles would almost certainly need to be replaced with either canals or railways carrying tons for potentially hundreds of miles. But that doesn't mean you can skip over them.

[Vinyadan]

Personally, I would focus on producing energy. Once you have it, you can use it for transportation, heating, metallugy, resource extraction, and so on, all while reinvesting a part of it it into improving energy production, freeing hands and brains to do other jobs. I don't really have a roadmap, but huge jumps in industry production and standards of living came from the availability of energy.

It's also a matter of the size we're looking at. If it's a world crisis, then underground machines used for coal extraction might still be in good conditions, and there would be a lot of brains going around. However, if it's a plane that crashed on a deserted island, things get more difficult: there is no certainty that coal, iron, or other metals, or really any specific resource will be available. I guess that, in such a case, the focus would be on making a boat and looking for somewhere better.

[Rynjin]

This was more or less the concept behind the british TV show Connections:

https://en.wikipedia.org/wiki/Connec...h_documentary)

Obviously it probably had gaps, but the idea was there. There was a book, I don't know whether it's still in print.

There is also the manga/anime Dr. Stone with a similar premise.

[tomandtish]

The original Mysterious Island (Jules Verne novel NOT any of the movies) addresses this somewhat. While they do get occasional help with found items, there is a fair amount of "We have to do this before we can do that".

[Storm_Of_Snow]

Personally, I would focus on producing energy. Once you have it, you can use it for transportation, heating, metallugy, resource extraction, and so on, all while reinvesting a part of it it into improving energy production, freeing hands and brains to do other jobs. I don't really have a roadmap, but huge jumps in industry production and standards of living came from the availability of energy.

However, you need certain techs to be able to generate power, so again, you've got to build to it. You can start with a waterwheel or a basic windmill made from wood (assuming you've got something to cut the tree down, then can turn it into planks and dowels) and use those start running small forging hammers and the like, but anything involving steam will need iron and steel to contain the pressures required to get anything useful from it, and if you want electricity, well, that's a few levels even more complicated.

To say improvements in industrial production and living standards came from energy availability isn't even half the story - it was also necessary to improve materials in order to be able to generate the power, while improvements in agriculture and medicine allowed for population densities which made such power generation investments economically viable, not to mention making sure the engineers and scientists working on them would be alive and have the time available to actually do it.

[DavidSh]

Of course, you can potentially shorten how long you need to rely on some of the technologies - you only need bronze tools until you can make iron in sufficient quantities and those iron tools can themselves be replaced with steel at some point, while a horse/ox drawn cart carrying materials weighing in the 10's to 100's of pounds for a few miles would almost certainly need to be replaced with either canals or railways carrying tons for potentially hundreds of miles. But that doesn't mean you can skip over them.

I think you can skip over the bronze. You should be able to mine bog iron and smelt it in a bloomery with stone tools, if you know how, and you have the right kind of bog handy.

[halfeye]

There is a theory that the more you know the faster you are able to learn more, up to the limits of human capacity to learn. Which mplies that the rate of change will keep accelerating.

[warty goblin]

I think you can skip over the bronze. You should be able to mine bog iron and smelt it in a bloomery with stone tools, if you know how, and you have the right kind of bog handy.

Bloomery iron is limited, particularly in terms of making large pieces of metal. It is also more difficult to work - and much more difficult to mass manufacture - than copper alloy because until you get basically modern capabilities you can't cast it, or you are limited to quite brittle cast iron.

It also isn't much better than tin bronze, at least in early form. And the vast quantity of fuel required to smelt and forge iron means you probably aren't setting up iron working in a society that couldn't support copper mining/smelting, regardless of where you source your iron.

[Willie the Duck]

The original Mysterious Island (Jules Verne novel NOT any of the movies) addresses this somewhat. While they do get occasional help with found items, there is a fair amount of "We have to do this before we can do that".

Also Robinson Crusoe and Swiss Family Robinson, although in both cases it's pretty limited to handwavium (neither author was an actual expert in such endeavors). Lots of log-and-rope buildings, but some of the stuff gets pretty impressive (IIRC the SFR eventually make a makeshift scuba-like suit).

Also any number of Youtube channels are dedicated to one or more components of this.

Bloomery iron is limited, particularly in terms of making large pieces of metal. It is also more difficult to work - and much more difficult to mass manufacture - than copper alloy because until you get basically modern capabilities you can't cast it, or you are limited to quite brittle cast iron.

It also isn't much better than tin bronze, at least in early form. And the vast quantity of fuel required to smelt and forge iron means you probably aren't setting up iron working in a society that couldn't support copper mining/smelting, regardless of where you source your iron.

Agreed. Until you are a society highly-proficient in ironworking, the primary benefit it has over bronze is not having to source the two minerals, particularly if you wanted to do casting. That said, if we're talking about someone with the downstream know-how, I wonder how hard it would be to skip right up to blast furnace ironworking?

[warty goblin]

Agreed. Until you are a society highly-proficient in ironworking, the primary benefit it has over bronze is not having to source the two minerals, particularly if you wanted to do casting. That said, if we're talking about someone with the downstream know-how, I wonder how hard it would be to skip right up to blast furnace ironworking?

China has been using blast furnace technology since like 500 BC - as evidenced by cast iron tools from this time. So it's clearly doable given an already organized state capable of iron mining, making lots of charcoal, etc.

But I'm not sure that gives you much advantage really. You get cast iron from the blast furnace, so you can cast stuff with is cool and all, but cast iron has ridiculously high carbon content and is stupidly brittle. So then you need to de-carborize the cast iron into wrought iron, which you can use for tools that need to survive impact. This is better than bloomery production - once they figured this out the Chinese don't seem to have ever looked back at bloomery smelting - but it clearly doesn't set you up for a super early industrial revolution because China didn't do that. You get mildly better steel and one piece soup pots.

The principle difficulty in kickstarting an industrial revolution is that for most of agricultural history labor (particularly low skill muscle power) is cheap, but materials and finished goods are expensive. You need a lot of materials and a lot of high end finished goods to set up an industry not powered by muscles. Which means you need vast wealth, and at some point a market. Trade is very old, but also slow and expensive for a long time, so it tends to mostly be high value goods, which isn't what industry does well, particularly early on. If you can only sell in a couple hundred miles before the transport costs make local production cheaper, its probably hard to recoup your costs.


So if you could set yourself up as a super rich Roman patrician or something, you might have a shot. You have the bankroll, the property, the trade network, and the huge urban center marketplace that could make an industrial undertaking eventually pay off.

But, like, good luck setting yourself up as a wealthy patrician out of the blue.

[Fat Rooster]

I think you can skip over the bronze. You should be able to mine bog iron and smelt it in a bloomery with stone tools, if you know how, and you have the right kind of bog handy.

You could, but if the intent was accelerated progress you probably wouldn't want to. Iron is better for items that need to be stronger, or take higher temperatures, but that basically means weapons and engines. For everything else bronze is easier to work with.

I think the tech tree would be far less of a tree than most people think, or at least much more abstract. There is a lot of "this would be much easier if we did x first", but there are surprisingly few actual 'things' required. Basic air steelmaking is actually a good example of something that isn't actually that hard to do once you realise how. Building a furnace that you don't need to spend a week rebuilding every time you use it is much harder, but there is a natural gradient towards that once you have the basics figured out, and there is no competing technology that is fundamentally more limited.
Abstract understanding such as Maxwell's laws of electromagnetism naturally branch out to many techs that don't need anything really advanced to take advantage of. With copper wire, glassmaking, and a vacuum pump, you can build machines from motors to lightbulbs to magnetrons. The technologies are often pure knowledge checkpoints, rather than improvements in manufacturing capability.

The first challenge that makes a tech tree difficult is that many of the connections are not really strict. We could have discovered lasers centuries ago, if there were natural lasing crystals. We could have discovered electric motors as soon as we had copper. Glass has great properties for studying chemistry, but other materials work. Does that make glassware a prerequisite for chemistry, or was it possible without it? Do we regard communication between scientists as a requirement? Writing and the printing press have made progress vastly faster, but are they actually required for other techs?
The second challenge is identifying other routes that may have been possible. What would have been the consequences of very early discovery of optics and photography? Could we have gone down the lithography path to build microelectronics without ever finding an easy way of making steel?

[Rynjin]

We could have discovered lasers centuries ago, if there were natural lasing crystals.

Could have? You dare doubt the awesome might of Archimedes?

[Willie the Duck]

China has been using blast furnace technology since like 500 BC - as evidenced by cast iron tools from this time. So it's clearly doable given an already organized state capable of iron mining, making lots of charcoal, etc.

But I'm not sure that gives you much advantage really. You get cast iron from the blast furnace, so you can cast stuff with is cool and all, but cast iron has ridiculously high carbon content and is stupidly brittle. So then you need to de-carborize the cast iron into wrought iron, which you can use for tools that need to survive impact. This is better than bloomery production - once they figured this out the Chinese don't seem to have ever looked back at bloomery smelting - but it clearly doesn't set you up for a super early industrial revolution because China didn't do that. You get mildly better steel and one piece soup pots.

Right, sure. But then let's move that up a step. Get the blast furnace for uniform pig iron and then implement wrought iron instead. I'm just trying to make DavidSh's idea of skipping over bronze feasible.

The principle difficulty in kickstarting an industrial revolution is that for most of agricultural history labor (particularly low skill muscle power) is cheap, but materials and finished goods are expensive. You need a lot of materials and a lot of high end finished goods to set up an industry not powered by muscles. Which means you need vast wealth, and at some point a market. Trade is very old, but also slow and expensive for a long time, so it tends to mostly be high value goods, which isn't what industry does well, particularly early on. If you can only sell in a couple hundred miles before the transport costs make local production cheaper, its probably hard to recoup your costs.

This is the fundamental problem with any and all of this. Much of the benefits of these innovations mostly benefit a society that has been slowly working up to them, and probably look like fool's errands to anyone who hasn't seen the immediate subsequent problem each was invented to address (wildly divergent example: traffic lights don't show how they are useful until cars on streets hit critical mass).

So if you could set yourself up as a super rich Roman patrician or something, you might have a shot. You have the bankroll, the property, the trade network, and the huge urban center marketplace that could make an industrial undertaking eventually pay off.
But, like, good luck setting yourself up as a wealthy patrician out of the blue.

I think that's why (ex.) Twain set up his Connecticut Yankee as quickly wowing a king and using that wealth/cachet to implement his incredible technological reforms. Some crank in the wilderness saying how they have magic knowledge that would revolutionize your life and save all sorts of labor, extend lifespans, fight cold/starvation and whatnot -- but you have to do all of it and have it all up and running before you see much benefit -- isn't going to convert a lot of people.

[warty goblin]

Right, sure. But then let's move that up a step. Get the blast furnace for uniform pig iron and then implement wrought iron instead. I'm just trying to make DavidSh's idea of skipping over bronze feasible.

If you know how to mine iron ore and build a bloomery smelter, you can skip bronze, there's no need to go for a blast furnace.

But you still need a society capable of producing the required raw materials, namely bricks, iron ore, and just hideous amounts of charcoal. All of this can be done in a settled stone or copper using society - if they're smelting casting copper they already have all the materials and production capability set up, you just need to convince them to mess around with other rocks. So Old Kingdom Egypt, the Maya and so on would be quite capable of going iron age given the knowhow.

This is the fundamental problem with any and all of this. Much of the benefits of these innovations mostly benefit a society that has been slowly working up to them, and probably look like fool's errands to anyone who hasn't seen the immediate subsequent problem each was invented to address (wildly divergent example: traffic lights don't show how they are useful until cars on streets hit critical mass).

The nice thing about iron is that, while not immediately particularly superior to bronze, it is useful to pretty much any society that figures it out. Nobody goes back to stone if they can get iron.

The difficulty is that iron age civilization does not tip over into industry at all quickly or readily. So sure you can teach Pharoah Khufu how to build his great pyramid using iron chisels instead of copper, but that doesn't mean that 2500 years later Augustus is going to fight the battle of Actium in ironclads.

I think that's why (ex.) Twain set up his Connecticut Yankee as quickly wowing a king and using that wealth/cachet to implement his incredible technological reforms. Some crank in the wilderness saying how they have magic knowledge that would revolutionize your life and save all sorts of labor, extend lifespans, fight cold/starvation and whatnot -- but you have to do all of it and have it all up and running before you see much benefit -- isn't going to convert a lot of people.

Yeah, in a lot of ways the social aspect is the absolute hardest, and it gets worse the farther back you go. If it's a hundred years or whatever, you just take some gold, pawn it, buy some stocks or make a good sports bet, and you'll be at least set up comfortably enough to live. You'll be a weirdo with odd social habits and a strange accent, but you could plausibly learn enough about the time period before going back to not seem a total idiot, and you can actually speak and read the language. But a thousand years, or 4000 years? You're an incomprehensible person with no clue what's going on, a total lack of ability to do even normal things, and deeply bad knowledge of local customs and so on.

[Tyndmyr]

Robinson Crusoe and similar sorts of tales are basically this. The protagonist is generally isolated, and has knowledge, but only enough starting equipment to keep them initially alive while they scramble for survival.

Perhaps one could consider The Martian a sort of similar tale, even though in this case nature is less a part of it than repurposing.

One limitation to this is scale. A single individual, or even a family could not create, say, a CPU manufacturing plant. Certain levels of technology require that society be at a certain scale.

This can strike much, much earlier than the computer era, in part because of specialization. One guy attempting to master every skill and to build his own tools for each runs into some hard time limits. A significant proportion of time must be spent in gathering and storing sufficient food, and even if one has read of advances like a watermill and has the concepts down, the actual crafting will pose some difficulties to someone who has never done it before.

There might also be locality based limitations, even if you can get a pretty good population. On an island with no iron deposits or coal? That's a hard limit unless you want to sail elsewhere. Polynesian culture has dealt with a lot of this, but it's not particularly easy, and can greatly increase the difficulty of developing heavy industry. So, it at least partially depends on where you are.

[Storm_Of_Snow]

I think the tech tree would be far less of a tree than most people think, or at least much more abstract. There is a lot of "this would be much easier if we did x first", but there are surprisingly few actual 'things' required. Basic air steelmaking is actually a good example of something that isn't actually that hard to do once you realise how. Building a furnace that you don't need to spend a week rebuilding every time you use it is much harder, but there is a natural gradient towards that once you have the basics figured out, and there is no competing technology that is fundamentally more limited.
Abstract understanding such as Maxwell's laws of electromagnetism naturally branch out to many techs that don't need anything really advanced to take advantage of. With copper wire, glassmaking, and a vacuum pump, you can build machines from motors to lightbulbs to magnetrons. The technologies are often pure knowledge checkpoints, rather than improvements in manufacturing capability.

Agreed - it's less a tree, more like throwing a load of different coloured wool skeins into a cattery, leaving it for several months, then pulling the resulting tangled mess out

If you know how to mine iron ore and build a bloomery smelter, you can skip bronze, there's no need to go for a blast furnace.

But you still need a society capable of producing the required raw materials, namely bricks, iron ore, and just hideous amounts of charcoal. All of this can be done in a settled stone or copper using society - if they're smelting casting copper they already have all the materials and production capability set up, you just need to convince them to mess around with other rocks.

Agreed, but it's also the tools you need to produce the processed materials, or the tools you need to make those tools - a blacksmith can't have iron tongs to hold the work piece while he hammers it until he's made them, so he needs something in the meantime.

So Old Kingdom Egypt, the Maya and so on would be quite capable of going iron age given the knowhow.

Potentially, but you'd also need to lead them down the correct path and make sure they used that to keep advancing on those lines - how many of the greatest minds of their ages basically wasted time on alchemy or other subjects that were eventually proved to go nowhere. Or created something that someone else had already created 100 miles away, but because there was little communication, they didn't know.

And then you'd have to make sure that civilisation survives to enable those advancements to carry on - while the fall of the roman empire didn't stop all advancements, it certainly slowed things down and potentially meant things needed to be rediscovered.

And we can still see some of this today, because we don't know what's going to work, so we try loads of things.

For instance, maybe Space X's work on reusable rockets will be rendered irrelevant if the Skylon concept works and makes payload to orbit much cheaper with the whole platform being reusable, not just one part. Or maybe Skylon's something that's never going to be practical. And maybe both will be superceded by someone figuring out how to get a working space elevator.

[warty goblin]

Agreed, but it's also the tools you need to produce the processed materials, or the tools you need to make those tools - a blacksmith can't have iron tongs to hold the work piece while he hammers it until he's made them, so he needs something in the meantime.

Surprisingly you can work iron using wooden tongs - I had figured this impossible but have seen people do it. They don't last a long time, but wood is cheap and only really needed until you get iron tongs. Which require a hammer, an anvil, and a drift to punch the hole for the pivot pin. The drift probably needs to be iron as well, but that's just a pointy iron rod, which itself only takes hammer and anvil. Both hammer and anvil can be stone, stone anvils actually persist a very long time into the iron age.

Potentially, but you'd also need to lead them down the correct path and make sure they used that to keep advancing on those lines - how many of the greatest minds of their ages basically wasted time on alchemy or other subjects that were eventually proved to go nowhere. Or created something that someone else had already created 100 miles away, but because there was little communication, they didn't know.

And then you'd have to make sure that civilisation survives to enable those advancements to carry on - while the fall of the roman empire didn't stop all advancements, it certainly slowed things down and potentially meant things needed to be rediscovered.

This you flatly cannot do. Akhenaten had the tremendous advantage of being a literal god-king, and his changes died about ten minutes after he did. There is no way to guide a society after you die, and frankly it's nearly impossible before for most people before that.


The best you can do is provide a very temporary shock, and hope it matters. Personally I'd go for things that do not require a particularly advanced technology to produce, but drastically improve productivity. Also ideally improve the lives of most people, rather than hand out improve tools for dictatorship simply because the lives of people on the way to industry still matter.

Iron working I have already mentioned. This helps because stone tools just aren't as good. You can link this up with wind/water power for power hammers, which are quite an improvement over hitting things with a boh sledge all day.

The spinning wheel is probably the biggest single labor saving device possible to introduce to a pre-industrial society. And any culture capable of building a chariot or wagon with spoked wheels can do it. It also mostly benefits and improves women's work, which seems quite worthwhile.

A related, but slightly less important technology would be floor looms with heddles, rather than vertical, warp weighted looms. The productivity gain is less than the move from a drop spindle to a wheel, but it is still considerable.

As a further bonus, textiles are about the first things to be industrialized, so simply having heddle looms and spinning wheels around seems like a useful precursor state to industrial production. I believe looms can also be run via water power.

Similarly, knitting is quite recent, and quite easy to bring back and teach to any society that is producing thread or yarn. Less an over production upgrade, more a quality of life improvement - fitted knit socks are great.

Animal intestine condoms are a very good idea. Allowing even some degree of family planning would be firstly a huge benefit to people. It also might go a ways to decreasing the enormous surplus labor pool of peasants trying to feed too many mouths on too little land, which would drive up labor costs. That in turn tends to encourage automation as a cost saving method. And again, fewer children starving to death or women dying giving birth to their 12th child in 15 years is just, on its own, a good thing.

(This is not ideal, both from a reliability view, and also because male-targeted birth control is going to be less effective, particularly on highly patriarchal societies. But unless somebody knows how to compound progesterone using common ancient world ingredients, it's the best I've got. I suppose copper IUDs are technically possible, but implanting them seems genuinely nightmarish given, say, bronze age gynecology.)

Depending on when you are aiming to go back to, there are other innovations like the horse collar and mouldboard plow that could be very relevant. Figuring put good crop rotations is another excellent technique to bring back, but that needs to be very specifically targeted to a given time and place.

Most of these do not require huge or complex devices, or vast amounts of super rare resources, or getting people to spend years doing weird stuff for no immediate benefit. The tools and infrastructure can all be done by carpenters, masons, and other people using their more or less existing skills. This should make them durable against things like empires falling, because they can be done as decentralized folk industries. You might need Rome to build roads, but you just need a carpenter to make a spinning wheel.

Water power is probably the biggest reach of these, because it requires entire complex buildings. It's also a very old technology that took a long time to become prominent, suggesting it offers relatively little value to the (unfortunately) serf/slave based economies of the ancient world.

[Vinyadan]

And then you'd have to make sure that civilisation survives to enable those advancements to carry on - while the fall of the roman empire didn't stop all advancements, it certainly slowed things down and potentially meant things needed to be rediscovered.

In particular, it led to massive cultural losses. It's not just a matter of belles-lettres: texts about agriculture, the military, and especially mathematics were lost. Through Alexander, the Greek world had gained access to some of the scientifically most advanced areas in the world (India, Mesopotamia, Egypt) and this allowed the production of advanced theories and devices. Much of this knowledge wasn't picked up or maintained by the Germani or even the Arabs, and we still are rediscovering treaties by Archimedes (I believe the last was from less than two years ago, although I can't find the articles I had in mind; a major discovery happened in 1906). Even when monasteries preserved a copy, it might have been outside their field of interest, and so it was overwritten; in the Latin West, Greek wasn't generally understood even by intellectuals until the XIV-XV centuries, which created another hurdle (and made the few translators very influential).

[Bohandas]

Animal intestine condoms are a very good idea. Allowing even some degree of family planning would be firstly a huge benefit to people. It also might go a ways to decreasing the enormous surplus labor pool of peasants trying to feed too many mouths on too little land, which would drive up labor costs. That in turn tends to encourage automation as a cost saving method. And again, fewer children starving to death or women dying giving birth to their 12th child in 15 years is just, on its own, a good thing.

This is a non-starter without introducing semi-modern medicine and sanitation first. People back in the day had twelve children because eleven of them were going to die from something that we would handle with vaccines, antibiotics or water treatment

edit: I guess it could also work if you had a tight enough plan and enough preexisting people to get things up and running to the point where productivity decouples from population within a single generation. That was indeed my original intent, but a lot of people here seem to be saying it's unfeasible with any amount of preparation.

[Smoutwortel]

I would focus on life extension(farming for food, peniciline for basic medicine, etc.), because having lots of people really helps with coming up with new wayse of doing things and it can also help extremely with obtaining the resources to build more things.

[Willie the Duck]

Animal intestine condoms are a very good idea. Allowing even some degree of family planning would be firstly a huge benefit to people. It also might go a ways to decreasing the enormous surplus labor pool of peasants trying to feed too many mouths on too little land, which would drive up labor costs. That in turn tends to encourage automation as a cost saving method. And again, fewer children starving to death or women dying giving birth to their 12th child in 15 years is just, on its own, a good thing.

(This is not ideal, both from a reliability view, and also because male-targeted birth control is going to be less effective, particularly on highly patriarchal societies. But unless somebody knows how to compound progesterone using common ancient world ingredients, it's the best I've got. I suppose copper IUDs are technically possible, but implanting them seems genuinely nightmarish given, say, bronze age gynecology.)

Thread topic has kinda drifted into time-traveler reinventing modern society early, so I'll stick with that premise. Starting there, an idea might be to find Silphium and make sure it isn't driven to extinction. We of course don't know how effective it really was, but as a suspenders & belt combo with lambskins, it should go a long way. Obviously comprehensive family planning, education, and then addressing the child mortality and other factors which incentivized large families would help as well.

[Bohandas]

This you flatly cannot do. Akhenaten had the tremendous advantage of being a literal god-king, and his changes died about ten minutes after he did.

Akhenaten negated the premise of his power.