With this post I wanted to make you aware of the Sapiens game as well. In terms of graphical rendering, it renders a complete planet pretty well with several LOD layers and a simple but realistic enough looking style and animations. That rendering and your underlying world engine might be a great combination. I'm not sure if this is at all a (technical) possibility but wanted to let you know.

It is an educational game that allows you to evolve creatures from an evolutionary chart (Evolution The Game of Intelligent Life tree of life - Imgur) in a historic or randomized evolving world (with the only attributes being terrain type and temperature).

It struck me that your "world engine" may be(come) very suitable for a (fan) remake of this game. In my creative mind's eye it could even be a prologue, making SotE span biological ànd cultural evolution. One could imagine a historical mode with existing species and a fantasy mode with all kinds of species. This leading up to the starting species in the cultural evolutionary part of the game as I have seen in your current project. /end brainstorm

I myself am unfortunately not skilled in programming and can therefore not assess very well if this is a feasible suggestion. I would love to hear your reaction.

But lets get on to the suggestion. From all i know this isn't a discussed feature currently, Now bare in mind, i am not on the discord, so i'm only going off the wiki, which is extremely bare-bones on the subject. Also, please note that the mechanics i am suggesting are using post stone age religious categories though it is possible that the mechanic could be applied to stone age religion, though i do not know enough about the subject to know for sure.

Now the hardest thing about designing a system for religion is that religion is a very complex subject dealing with the morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, and organizations of a wide variety of cultures.

Now because of this i think that any system related to religion shouldn't just be some random name which pops follow like EU4, and it should be more complex relating to a religion's theology and practices allowing for dynamic change throughout the eons, basically it should be its own unique part of the game and not just some vague and random name with buffs and debuffs.

Also it's in my opinion that specific religious categories and beliefs like mono or polytheism shouldn't be tech tree nodes like stone tools, because if that is mishandled it could make it look like the game is making statements favoring one belief or others. The best situation in my opinion is the emergence of specific religious categories with the emergence of the first religions which would be under those categories.

though i wouldn't mind Religion itself  being a node which symbolizes the emergence of more and more complex spiritual beliefs among the various species of a SOTE world, and this node could lead to the unique mechanics of religion.

Now for how to categorize the specific religions of a world, i think that the best system would be that there are what i'll call "belief bases", basically an essential belief multiple religions can share like Zoroastrianism and Judaism both believe in one god. i would design these bases around how many spiritual beings a religion worships, it would start with worshiping a multiple of gods (Polytheism) to worshiping one god (Monotheism) to worshiping no gods (Non-theism) "but how would religions in the same base differentiate themselves?" You may ask, well that's where we get into the religion trees. Now there would be 3 trees for each of the three bases, and would and would be similar to a tech tree, but instead of technology it's the beliefs, structure, and other aspects of the religion, allowing for a wide variety of differences even among religions which share a belief base, though i would lock some nodes behind technology like a Religion can't have a holy book if they haven't invented writing yet, and because of the they would stuck with an oral tradition.

"but how would do you simulate ideas which two bases can share, like monolatry?" (monolatry the belief in the existence of many gods, but with the consistent worship of only one deity)

that could be solved by what i call "syncretism trees". These trees would allow religions in neighboring bases to have beliefs which multiple trees could share, For example, henotheism, Though i'd probably lock most syncretism out unless religions of neighboring belief bases have contact

I would appreciate any comments or criticism you have of my idea.

and also, Thank you for reading my suggestion!

Edit: I made some improvements to my post and i added an idea if religon is in the tech tree.

Edit 2: I've fundamentally changed a lot of the beginning and i've cleared up some things in the mechanics suggestions

Edit 3: 100 VIEWS!

 The most recent DLC for Warhammer II gave me an idea for a race. I call them triffids in honor of the classic science fiction movie (and not the newer drivel). After some discussion on the Discord server, I think I have determined enough of the details to write a longer description to be posted in a more permanent location, i.e. this forum.

The idea is to have a completely feral race of sentient plants which can only survive in the wilderness. This race would die in urban environments and would thus seek to protect forests, swamps, grasslands, and other plant-rich areas while destroying civilization which disturbs them. They would be a force which directly opposes the civilized races. Other feral races would fit well with them, and elves would be a special case of a civilization that the triffids could bear, if handled appropriately.

The triffids themselves are all connected via roots (like aspen forests) and thus share nutrients. They would be a "hive mind" of a sort. I know this is a trope in science fiction and fantasy, but here it makes more sense because the triffids are physically connected. Like the triffids from the story, these can spit acid and locomote. However, they prefer to remain stationary. They have thick bark and vicious spines protecting them from physical attack, and their heavy sap is a deterrent to fire and disease. Attached to them are vines which they can lash like whips. If necessary, they are capable of quick bursts of speed to chase an intruder or escape danger (such as the obvious problem of civilized races using fire to just burn them, again like the movie). Like kudzu, they aren't too big of a problem if managed, but if the civilization is weakened and can no longer keep them in check, they will grow wildly and transform the settlements and farms into their vegetative playgrounds.

They reproduce exclusively via sprouting from roots. That is, they do not generate seeds or sexually reproduce in any way. This makes migration very slow and difficult for them. Scouring their roots from the land is a certain way to remove them, but their roots are deep and tough. Thus, they become entrenched in areas they control, but have difficulty spreading. Because they are plants, they need plenty of soil nutrients and water. The intelligence of a grove is based on the number of its members. They also don't develop much technology on their own, but they can trade with other races for things they cannot produce. This could lead to a situation where triffids begrudgingly allow some civilzation to exist in order for goods they want to be produced. Triffid groves might quarrel just as ant colonies do, as groves with different root networks are separate societies.

 I wanted to design a desert-dwelling race that was unique and interesting. After some deliberation, lizardmen seemed the best option. Although this concept might be overly long and detailed, I think that it merits extensive explanation.

The reptilians have a mix of features from many reptiles, though the largest influence was komodo dragons. Think of reptilians as bipedal komodos. Real komodos can stand on their hind legs briefly, and they look pretty goofy doing it.

Reptilians are ectothermic and therefore can only live in cool in environments with great difficulty. Cold areas (particularly below freezing) are uninhabitable for them. However, reptilians can lie dormant and nearly motionless, allowing them to live in areas which are warm in the summer and cold (but not freezing) in the winter, as they can remain inactive during the cooler months. Because they do not have to generate their own body heat, their metabolism is very low. They can thus live without food for long periods, much like crocodiles. If the ambient temperature is high, they can devote a much higher proportion of their calories toward purposes other than thermic homeostasis. This makes them specialized for warm environments, but reptilians prefer no particular warm environment. Thus, reptilians are selective generalists, able to survive so long as the temperature is high. Clothing is not especially important to them, as they have little body heat to retain and their scales already offer protection.

Reptilian metabolic versatility has a significant cost, however. Nervous systems, and particularly brains, are energy-intensive and require relatively high metabolism to maintain. Lacking this, reptilians do not develop large brains and are therefore quite unintelligent, though they still are among the intelligent races. If humans have an intelligence of 100, then reptilians are somewhere around 60-70. They thus tend to be more feral than civilized. They are capable of hunting/gathering and herding, but achievements of greater intellectual fortitude (cities, complex governments, infrastructure) will likely elude them or only be shallowly developed. However, reptilians can easily live for over a century, again due to their low metabolism. Thus, individuals can accumulate knowledge, so reptilian civilization is certainly not impossible.

The largest reptilians can be monstrous, but many are not significantly larger than a human. A reptilian's size is largely determined by the available nutrition during its maturation. Reptilians living in remote deserts with scarce food will be smaller, while those dwelling in lush and hot jungles will be mighty beasts. The reptilians are very tough (due to muscles and thick, scaly skin) and capable of high strength and agility, but only in short bursts. They thus have low endurance. Low metabolism means that signficant time is needed for an exhausted reptilian to recuperate, but a fresh reptilian can easily crush bones. Their dexterity is also quite low, as their hands are akin to those of komodo dragons: thick, ponderous fingers tipped with large claws unsuited to fine manipulation. Reptilians are obligate carnivores. They find plants indigestible, but livestock can consume them, thereby transforming plants into meat. Reptilians are bipedal and terrestial. Though they are not unimpressive swimmers, their low stamina renders them unable to traverse long aquatic distances.

Whether r- or K-selection is prevalent depends on the circumstances. The number of eggs laid by a female is determined by her nutrition. In times of plenty, when she is well-nourished, she will lay many eggs. In times of scarcity, she will lay only a few.

Reptilians use the ZW sex determination system, which can be seen as the opposite of the mammalian XY system. Among humans, two of the same chromosome (XX) produces a woman, while differing chromosomes (XY) produce a man. The Y chromosome is smaller and modifies the X, meaning that the base form is female and men are modified women. In the ZW system, two of the same chromosome (ZZ) produces a male, while differing chromosomes (ZW) produce a female. This means that the male is the base form and females are modified males. This is significant because it allows parthenogenesis, i.e. reproduction without fertilization. Komodo dragons are an example of this; a female can lay eggs which will hatch into males who can then mate with her once they are old enough, thereby producing more females to create a stable population. This functions because the female (ZW) can produce offspring by herself with either ZZ or WW chromosomes. WW is not a viable combination (like YY among mammals), so only the ZZ (male) eggs hatch. Their Z chromosomes can then combine with the mother's W chromosome. Among mammals, females only have X chromosomes, so a parthenogenic mammal could only produce daughters. This could lead to interesting cultural conflicts in the game wherein reptilians do not disapprove of incest while other races find it barbaric. This sex determination system also means that reptilian populations are extremely difficult to displace, as even one female can eventually produce a stable population (though with a severe genetic bottleneck).

I imagine reptilians inhabiting uncivilized equitorial regions such as jungles and deserts. They are exceptionally well-suited to hot environments with widely varying food supplies. Places that would fry other races would be comfortable for reptilians, meaning that they could continuously inhabit certain areas without ever being displaced, as no other race is interested in those areas. Thus, they are left and can develop low-intensity civilization. Perhaps there could even be the odd reptilian who is super intelligent. This could combine with the long lifespan to create a powerful leader who brings about a golden age of reptilian might based on a fertile river or desert oasis.

Shellfolk would be quite tall at roughly 6-7 feet in height, and in place of flippers, they would have long limbs, possibly with webbed feet and hands(?). They would be able to hold their breath for many hours (some sea turtles can go without air for close to half a day, although I'd imagine a larger creature would need oxygen more frequently).

They would be omnivores and mainly subsist off of seagrasses and seaweed, as well as both shallow water and deep sea fish, crustaceans, jellyfish, cephalopods, etc. 

They would be highly k-selected and nomadic, have a lifespan of hundreds upon hundreds of years, and would mature extremely slowly. Nomadic shellfolk would seasonally migrate along foraging and nesting sites, sometimes across thousands of miles between oceans.

Shellfolk would be capable of permanently settling on land, but would also require near-constant access to a body of water or they would die of dehydration over the course of several days. They would be stronger than a human, however they would obviously be very slow on land, making them poor raiders (except as pirates possibly).

Shellfolk would likely skew feral due to their small population and difficulties of living on land, though they’d be capable of forming long pockets of civilization along the coastlines of islands, major bays and rivers, wetlands, areas with seasonal monsoons, etc, with the largest of shellfolk cities being based around carefully managed and farmed estuaries. They could also form extremely defensible settlements on islands in the middle of lakes, similarly to Tenochtitlan in our world.

Terrestrial races could even employ shellfolk tribes as vassals to guard vital rivers or straits.

Assuming their shell is modeled after something like the above (covering both the back as well as the front), it would make shellfolk virtually immune to most attacks from behind or at the midsection, protecting them from predators and raiders. Their main weak points would be their neck, limbs, and head, areas commonly covered in armor. 

If forced into conflict, almost nothing would be able to overcome a formation of armored turtlemen defending an amphibious position (pre-gunpowder weapons). However, due to their generally peaceful attitude towards other races, along with their small population, stable politics, and long lifespan, shellfolk would often have a reputation as wise old pacifists.

If kappas stick around, they could have a pretty interesting relationship with shellfolk (presumably r-selected vs k-selected, entirely feral vs somewhat feral, raiders vs non-raiders, etc), but that's getting out of the scope of this suggestion and I probably already went too long.

Let me know if you have anything to add.

Mummies would be one of the few races that would inhabit Desertic biomes. They're quite an old race and they are very civilized (not to the point of High Beavers but more than Elves) and quite specialized too (to the same extent than Elves more or less). But they would be a very extreme example of K-selected race: live very long, and have very few offsprings. 

But why would a specie would just roll themselves in toilet paper? Well, Mummies are a race of beings that fed on magic. Temporal magic, to be more precise. They "eat" time to gain magical properties, but the downside is the rapid decay of their body. Their minds are still alive and sharps, but the body quickly became unable to support it; and since a mind without a body is basically useless, they have to put all their body in bandages to still be able to work. 

Since they are basically immortal and they feed on time, they are very conservative and subject to high hubris. Quite like Elves, but more cunning and with more distrust towards strangers. 

It's just an idea I launched because I thought having desert-biome races might be a good idea. I might expand it later if I have more ideas on it. And don't hesitate to give feedback and expand it yourselves! 

Mechanical Turchin Social Engine:
This is based largely on Peter Turchin's work on social dynamics. If you're interested, recommended reading is at the bottom. Turchin's insights can be boiled down to two key points:
1. Agrarian societies follow regular, endogenous, overlapping cycles. The longest of these, based on Malthusian dynamics, Turchin calls secular cycles. The downturn in a secular cycle is accompanied by great social unrest, often including civil war.
2. The level of social cohesion, or *asabiya* (after Ibn Khaldun), is extremely important to the success of any human group. Asabiya builds in the face of threat from an outside enemy. Asabiya reduces in each downturn of a secular cycle, and has a general tendency to decline over the long term.

These phenomena are very pertinent to SotE. I will give a more extensive, but still brief, explanation of how each one works according to Turchin, and how I think they could be modelled by game mechanics in SotE.

SECULAR CYCLES

Things are great for farmers as long as there is open land left to be cultivated. Every son can move out to found his own farm, and all can enjoy the same standard of living as their parents.

Things start to suck when you run out of new land to cultivate. If a family has 5 sons, there won't be enough land to go around, and each son will be living in poverty and precarity. If a bad year hits and he loses most of his crop, he will need to go into debt to feed his family. His farm will be the collateral. His creditor will likely be a nobleman, or another peasant who didn't have any siblings, and inherited a full-sized farm that can afford to loan out surplus.

If another bad year hits, the poor man loses his farm as collateral, and is now a landless laborer. The nobleman or rich peasant now has even more land. Iterate over a few generations, and you have a very unequal society, with a few very rich individuals, and a lot of landless poor. This situation is more or less inevitable once an agrarian society hits the Malthusian limit.

The poor keep getting poorer, because more landless laborers = more labor supply = lower wages. This usually leads to peasant revolts, but the upper classes, if united, can almost always put such a revolt down.

The upper classes, glutted with wealth (more land + lower labor costs), experience a brief golden age. This is when a lot of world-famous art is patronized. However, copious reproduction and ever-growing conspicuous consumption vastly increase the operating costs of the upper classes, while the agrarian economy that they skim off of isn't growing any more. Soon enough, the elites enter their own crisis. They need to spend like in the golden days in order to keep their status, but they are increasingly strapped for cash. They turn to the state for support, and turn on each other to monopolize state access among a sustainably small patronage network. In desperation, social cohesion falls apart. This is when you get a civil war, and possibly successful peasant revolts.

Conflict follows a generational "fathers and sons cycle", where one generation learns the horrors of war and eventually works towards peace, while their ignorant sons rekindle things one generation later.

This process continues until the underlying problem of elite overproduction solves itself, with fewer births (due to precarity) and more deaths (due to war) bringing the elite population back to healthy numbers. The elites have to die. If the literal Black Death hits and the peasant population falls well below Malthusian limits, this actually makes things worse in the short term, because the elites now have an even smaller economy to extract from.

Per Turchin, this process explains, in whole or in part, the late-republic Roman civil wars, the Crisis of the 3rd Century, the unrest all over Europe in the 14th century, the unrest all over Europe in the 17th century, and most other periods of intense internal instability in agrarian societies. The timeline of the rise-and-fall of Chinese dynasties follows the same frequency, and from what I know of it, the specifics seem to be in order as well, at least for the fall of the Western Han.

How does this translate into SotE? The following need to be modeled:

Rural carrying capacity/arable land still available for cultivation.

Economic inequality, either abstracted or represented as actual population wealth stats.

A natural process whereby poor pops become poorer and wealthy pops become wealthier when arable land runs out.

Pop fertility levels that match economic fortunes. This will naturally soft cap post-Malthusian commoner populations without reaching famine states, and it will naturally increase elite population even after the general population has stagnated.

Unrest as living standards decline. I'm sure you guys are planning on this already.

Conspicuous consumption (including art patronage!) among the elites as their wealth increases. Effectively, per-capita demand should grow with per-capita wealth, but NOT decrease with it under normal circumstances. As elite demand exceeds their ability to meet it, they should naturally shift into the same "angry and poor" state as the peasantry, despite not actually being poor. Then the fun starts!

When elites enter the "angry and poor" state, they begin petitioning the state for handouts and sinecures and other forms of support. They also divide into factions, centered around powerful men who promise gains to their dependents. Giving patronage to one faction causes the other faction to get angry, and undermines their support for the state.

When one faction's loyalty is low enough and an event sets off the powderkeg, they revolt. Ideally, the most powerful families within a state - as well as their local holdings/power centers - will be modeled, and the actual holdings/power centers of the rebel faction will provide the backbone of the revolt.

As the events of war cause general population decline, elite population should fall faster than the general population - they are more likely to be fighting and dying in battle, and are more likely to be targeted by rampaging armies, at least in per capita terms.

As war wages throughout a country, pops should grow war-weary, reducing unrest levels. The modifier should wear off completely within 20-30 years however, causing war to be rekindled until the underlying problem of elite unrest is taken care of.

At some point, elite demands need to come down back to normal levels. TBH, I don't know what specifically to peg this phenomenon to, but it needs to happen. Once elite pops are able to meet demands again, they should naturally leave the "angry and poor state", and all the plotting and feuding that undermined the stability of the state should vanish.

A side note: modeling elite unrest as a function of demand vs. ability to meet demand gives you lots of interesting ways to manage it, at least in the short term. A big war that brings in lots of booty might buy you the time you need to prepare for the shit really hitting the fan. If a disproportionate number of nobleman happen to die in that war, so much the better...

Now onto...

ASABIYA
This is going to be a lot shorter, because I'm at 2000 words already and I'm kind of tired.

Asabiya is, in a sense, a measure of how well the members of a society are willing to put the good of society ahead of their own private interests, or that of their family and friends.

Asabiya grows in the face of a threat from an outside enemy - Turchin uses the term metaethnic threat. The greater the threat, and the more alien the enemy, the better. Alienness can mean several things. Are they barbarians, with a fundamentally different social structure (and economic base, if they come from the steppe)? Do they follow a foreign religion, perhaps one that you especially hate?Gaulish barbarians attacking Rome, Vikings attacking most of Northern Europe, Qiang and steppe peoples attacking various (North) Chinese states, Muslims attacking Christian kingdoms in Spain - all of these supercharged the asabiya of the societies on the defense.
But asabiya declines over time. It hits temporary low points during the periods of unrest in secular cycles, but it never fully recovers to its previous point without a recharge from foreign threat. By the year 400, Italy was an asabiya black hole, as it had been the center of the Roman Empire for nearly a millennium. Asabiya in the Balkans, however, was constantly being recharged by barbarian threats, which goes a long way to explaining why so many late Roman emperors came from that region. Being from a society with high asabiya has important effects on individuals, and it tends to produce strong leaders. I don't think it's a coincidence that the Barca family had their base in wild and unpacified Spain, rather than in the African heartland of Carthage.

How to model all this mechanically?

I don't think there's a way around an abstracted "asabiya" modifier attached to each pop. Gradual decline can be modelled by having the unrest period of each secular cycle chip away at the base asabiya value (in addition to much larger temporary reductions).
Base asabiya would only be recharged by metaethnic threats, which could operate through several mechanisms. Are you at war with an alien enemy? Asabiya ticks up slowly over time for all pops, faster if the enemy is more alien. Are alien armies rampaging throughout your territory? Pops gain an asabiya boost proportional to the alienness of the enemy, the damage inflicted, the size of the enemy army, whether or not they experienced the horrors firsthand, and if not, how close they were from the carnage. Are your pops in a border region next to a metaethnic Other that you are not on good terms with? They enjoy a passive asabiya boost.

Asabiya should grow and fall logarithmically, so that - for example - border regions don't always hit max asabiya, and so that you don't immediately lose all social cohesion in the imperial core just because you made it safe. Looking at the Roman example, it should take about 6-800 years to deplete your asabiya battery under ideal circumstances (the last sack of Rome before Alaric was in 390BC, and I believe no foreign army seriously threatened Italy after Hannibal withdrew in 203BC).

That's all for now... I'll leave this at 3100 words. Thanks for reading! If you want to read more, I highly recommend Peter Turchin's *War and Peace and War* or *Secular Cycles* (*Secular Cycles* is very math heavy, *War etc.* is a more readable summary that doesn't get into the mathematical models). Turchin's book *Ultrasociety* deals with the origins of large-scale societies among humans, which is also highly relevant to SotE's simulation, but beyond this post.

So, one of the ideas behind SotE is the eventual decay of empires so the new ones can rise. One of the requirements for such system to work would be such a technology system that will have a built-in "forgetting" mechanic. And this is what I'd like to suggest.
The system I am imagining would have every technology have 3 values about how well it's researched, as opposed to one present in most games (researched = yes/no). These would be:
1. Discovery
2. Understanding
3. Reachability

Discovery would be the first step in researching the tech, essentially just your people realising that there is such a thing. Discovery could be implemented two ways: 1) it could have a chance(affected by other values) to be discovered every certain unit of time in-game or 2) it would increase by some percent(affected by other values) every certain unit of in-game time and is Discovered at 100%. But only discovering a technology is not enough to be able to make use of it.

Then your people will need to understand how to use that technology effectively. Understanding would range from 0% to 100%, and be slowly gained as your people are familiarizing themselves with and mastering that technology. And understanding that technology will be what directly affects its effectiveness - at 50% understanding, you will only get 50% of this technology benefit. Also, at certain tresholds, there could be bonuses that you unlock on top of getting just technology benefits, or these tresholds could be required for discovering further technologies. Also, there could be no scaling benefits from understanding, and only bonuses from reaching tresholds. The first treshold could also be set at 0%, making it available essentially as soon as discovering that technology.

Reachability would be information about how many of your people have access to that technology. It's implications would vary based on what the technology is. If it's some agriculture improvement technology, if only 10% of your people have access to that technology, only their production output will be increased. If it's military unit-unlocking technology, only 10% of your population will be possible to be recruited as that unit.

All these properties could be either country, province, tile or any other unit of scale wide.
And all these properties could also decline.
For example, if we take a technology "Plough". Let's say that it has a scaling effect of up to  +30% farming efficiency, and +10% at Understanding_Treshold=0%.

Discovery of it would depend on such things as how agrarian a society is. Once it's discovered, some of your people make them and start using them, but not very effectively - you have low understanding and low reachability. But the neighbours/relatives/whatever of people using plough see that it already boosts their output by a whooping 10% percent, and decide to start using them too(if it's not made impossible by for example lack of high quality wood necessary for making ploughs[if high quality wood is necessary for that, its just an example]) - your reachability is increasing. As more and more people are using ploughs, they share their experiences between themselves and figure out how to use ploughs more effectively - your understanding is increasing. All is good and you are getting close to getting a country-wide +40% total farming output bonus. But then the vermen attack. Most of the high quality wood is used to make weapons, leaving not enough to make ploughs to replace the ones broken over time or make new ones - your reachability is stalling or even decreasing. As your farmers are dying on battlefields, so is their knowledge on how to use ploughs effectively - your understanding is decreasing. Once you understanding and/or reachability is low enough, you risk forgetting a technology - un-discovering it. Another one or two hard wars with vermen and your farmers will abandon using ploughs. Being able to swing a sword will be more important for them.

All of the above changes could be made faster or slower depending on variety of things.

If your society is communal and/or lives in densely populated areas technology will reach more people faster, and vice versa - a solitary farmer in sparsely populated region won't go on a 5-day trip to his 4th cousin just to show him a new stick he has. 
If your species is long living, every individual can have quite a lot of time to familiarize himself with new things and pass on the knowledge he acquired. But on the other hand, conservative societies will look at new tools with distrust, and will prefer to stick to their traditions. An 150-year old Elven lord migh prohibit all people in his demesne from using "devilish stick of corruption", and few generations may need to come and go before its truly embraced as an useful too.
If you have enough high quality wood, or enough weapons in stockpiles, preparing for war will not necesarilly affect reachability of ploughs in your realm.
And if your society has developed a tradition for writing things down, you will not necessarily lose the knowledge of how to use ploughs effectively if 70% of your farmers die, as that knowledge would already be written down.

That I think sums up how such a technology system could work. But in the beginning I mentioned that maybe it's not only for technologies...
I think something like that could be implemented in many different aspects of a society.

This could be used for something like traditions, maybe with slightly altered names and maybe no discovery.
For example a "Warmongering" tradition could determine how much... warmongering your nation is. Without discovery, understanding would be renamed to "Strength", determining how big of an impact it has, and reachability to "Commonness", telling how many people are affected by this tradition. And if we stick to warmongering, it's effect scaling with "Strength" could be up to +20% damage and as a negative as low -10% defence at 100% strength. This could also implement bonuses at certain tresholds, for example at 60% strength you are able to recruit berserker units. 
Another thing this system I think could be used for, is adaptation to certain environments. Again, just rename "Understanding" to something like "Adaptation" and "Reachability" to something like... I think "Commonness" once again is the best fit, and make it determine how well your people manage in different environments.
As an example, "Mountain Life Adaptation".
Scaling with adaptation, you could get movement speed improvements, better mining output etc. At certain tresholds you could get bonuses like ability to make homes inside the mountain. 

Here's a few examples for how an interface might look like for such mechanic:
 

 
Big circle with icon inside it represents discovery. Upper bar represents Undestanding(books) and lower bar represents reachability(people).
Wheel is about halfway towards being discovered.
Warmongering is discovered, its at around 30% strength - at around 50% there's berserk unit unlock but that society/country is not there yet. Commonness is very high though, meaning a lot of people are warmongering, its just not very strong in them.
Mountain adaptation is high, and homes inside mountains are long discovered. Commonnes is not very high though, so not a lot of people will be able to make use of that.