A couple thousand years or so ago, the Roman Empire still breathed and bled the proof of its existence. Along her streets roamed scientists, artists, philosophers, emperors, et cetera and these people have left remnants which can still be observed today. Latin is used in medicine, law, and politics. Some schools teach classes in humanities and ancient literature, in which one is almost certain to find the hand or tongue of one of more ancient Romans. When North America was colonized, a spatter of government buildings were inspired by their ancient architecture. This was made possible by the fact that these ruins can still be observed and visited today.
But of course ancient Rome wasn’t the only old culture which left buildings still standing. Scattered around parts of Europe are stone churches that have been standing for centuries. Less harmful to the existence of the European culture are the centuries-old castles and houses. The former conjures up a mental image of a giant stone fortress – cold, gray, forbidding and indicating the position of power the ruler therein had been (often) born into. The houses are more varied.
Some people made circular houses (Celts were very skilled at this, and someone once built a house in this old-fashioned style to study its effectiveness, afterward reporting that it stayed cool in the summer and warm in the winter) while others preferred rectangular or square houses. It was easier to make the house either circular or square/rectangular depending on the materials used. Stones typically resulted in the house becoming square or rectangular while sticks made it easier to make the house in a circle shape. One mixture used to hold the materials together and provide insulation involved hay or straw, mud/clay, and animal hair. Notice how all of the materials were basically just stuff from outside.
No one officially taught the first builders of these things what to do to make a house. It’s possible that they watched birds building nests or beavers building dams and got some ideas from that, but generally it was a process of trial and error. Eventually they managed to excel so much at the process that they started making the afore-mentioned houses that have been standing for centuries. They likely passed on this knowledge to their descendants verbally and the knowledge of how to build was spread when people from different tribes or communities were wedded. At some point this knowledge was obviously lost.
It may make some people wonder how a population could transition from caves to houses, but that question isn’t worth much time. Agriculture was born and they built what basically amount to artificial caves on fertile soil for farming purposes. A question worth a little more time would be how intellectually sophisticated they had to be to do things like figure out how long the materials for the roof had to be to prevent it from collapsing, make patterns and designs out of rocks of different colors, and discover how to build windows and doors into what might otherwise be a solid wall – what’s more: where did they get the idea to bring windows into existence in the first place? A hole in the roof and the open door could both serve for light and ventilation, so what did they consider to be important enough for them to have to add windows? Watching livestock maybe? If this is true, then how much of a need do we have for windows? None if the ventilation is good enough to do without them. (If it is false, then perhaps we still have the same reason they did.)
So at some point people thought through all of that and decided what materials would be the best to build with. They decided what to combine and when as well as how to put everything together into a sturdy structure. Their resourcefulness and ability to think things through before acting allowed them to progress and make useful inventions we still use today (apart from the house they gave us things like the plow and the wheel). When intellectual abilities like those are removed, there can no longer be progress. A few people end up controlling industries and governments while most of the rest don’t know how to do anything by themselves and, as a result, become incapable of living independently of society. If the few people currently at the top of the pyramid stopped doing their jobs either voluntarily or involuntarily, these dependents of the current system would eventually die and leave the old-fashioned resourceful people capable of thinking for themselves almost alone. Nature would slowly start taking back the earth and only the intelligent, resourceful people would figure out how to survive ‘twixt her vengeful jaws.
Because of the possibility of various forms of this event, if would be worth it to prepare in advance. Be resourceful like the people of the olden days. Learn self defense in case someone breaks into your living residence. If you plan on building that living residence yourself, make sure it can stand up to intruders, the elements and the test of time. If you don’t grow or breed your own food, learn where to find it in the wild. Learn how to repair things like clothes and appliances and invest in things built to last. Consider getting some sort of guard dog. Try to think of lists of different ways objects can be used that you don’t normally use them for. Learn the art of starting a fire and gather supplies for emergencies. Don’t bother buying useless junk that will only weigh you down. Memorize useful things for if and when the time of their necessity comes, and this includes basic first aid. It’s better to be prepared by having something useful and not needing it, than to need it and not have it.