In my scenario, human civilization was blinded by some cosmic event analogous to the Tower of Babel. They are plunged back into the stone age and will begin to redevelop civilization
Is it possible to develop a civilization of only blind people? there are no sighted individuals as this is a genetic change.
This answer assume that the blind people are, as stated on the question, on a stone-age development state, and doesn't currently have access to modern times technology. If they do have access, please leave a note and I will change this answer accordingly.
Having eyes is one of the major adaptative features on earth animals. They enable you to work on environment while on a safe distance of anything dangerous. They enable you to find fruits, to hunt, to evade things that are hunting you, to read and write, to... well, a ton of stuff. If everybody would go blind, we would have so, so many problems that I doubt human race could survive five or six generations. Let's get into detail.
Imagine that you must grow wheat to survive. And you are blind. You must prepare the soil, distribute the seeds, check if the plants are ok from time to time, apply fertilizer if needed, and them, when they mature, harvest them.
Preparing the soil would already be a big problem. Without sight, you can't really tell were you are without some sort of reference point at hand-reach. And... in the middle of a huge wheat field, what you definitely doesn't have is a reference point at hand-reach. Even if you put landmarks from time to time with ropes scattered everywhere, how would you prevent yourself from getting lost? A big, huge farm is not the same thing as a complex urban environment with tons of different reference points scattered everywhere. Even middle and small sized farms would be an issue.
Tending the crops would be even worse. Without eyes, you wouldn't be able to tell the difference between weeds and wheat until is too late. Without eyes, you won't be able to check if the crops are okay or if they are sick. You can't tell if there are flocks of crows eating your crops. You wont be able to tell the difference between a good, edible fruit and a poisonous one if they are pretty similar.
Gathering food would be almost suicidal. If you go to the woods to pick up some berries, there would be tons of animals ready to bite, claw or sting you with no mercy. Go too close to a snake, miss that deadly scorpion over there, or run into a pack of wolves. Without eyes, you can't fight back. You would be food in a blink. Also, you can't run: Being blind and trying to orient yourself in the woods or any type of difficult terrain is almost impossible at a fast rate — you need to be constantly checking for obstacles to avoid tripping, and if you trip while running away from a bear — bye bye.
Letters are easy. You can write some stuff on paper and then it stays there, ready for you to read it later. Text is a fast, simple, and efficient way of storing information. Remove the eyes of everyone, and almost all the knowledge would be irreversibly lost. People would lose all sense of geography without maps, and even reaching another city would be a huge problem. Without the stars or the moon to tell you where you are and where are you going, overland travel and sea navigation would be impossible. Settlements would rarely enter in contact with each other, and would in turn become more and more isolated from each other, cultures diverging more and more, until you have two completely different peoples with even different languages.
Good eyesight is a must today, when we have the extremely advanced machinery to help us to treat people. If you have a blind doctor, by the time he finds the cut that you made on your leg while running away from the wolves you would already be dead.
I will keep this one short. How do you find your toddler? If you took a nap and that little brat escaped from his bed, how would you find him? He can be under the bed. He can be outside, in the garden. He can be on the belly of that mother-wolf that is tending a new litter of puppies — blinding all the humans would be a nice thing for them, that's for sure.
With eyes, we can see who is around us. Without them, you only would be able to tell if someone is there by their voice. Where are your loved ones? Where are your kids? Are they sleeping? Are they gone? Is there someone strange on your house? You can't tell if they don't produce some sort of noise. While you talk to someone else, who is listening? Are you sure that you are alone?
Keep in mind that having eyes is one of the most basic evolutionary traits of modern animals. Those that don't have some sort of vision normally inhabit pitch dark caves that wouldn't be a good place for humans. Losing eyes is a major setback that can destroy an entire population really quickly — even humans.
Note: For how to use your additional sense for skills like (long-distance) communication, growing food etc. see the second section of this post. The first section deals with how the additional methods of perception humans have are working.
EDIT: Please also watch this TED talk on sensory substitution and sensory addition. Seems like my ideas are not that far-fetched after all.
Have you ever heard of human echolocation ? If you didn't this might sound – pun intended – like some kind of superpower but it is actually possible to grasp your surroundings in the absence of functioning eye-sight by perceiving the resounding sound. Bonus: If you are not blind yet – you could have an accident in the future or a medical condition – this is even easier to learn as during your asyou can get more immediate feedback on whether you have successfully detected an object or not by taking a glimpse.
Meet the real life Batman Daniel Kish to get a better idea of this fascinating ability. He termed it FlashSonar and in another documentary one of his students was able to use it to detect the exact position of a metal rod about one inch thick from one and a half foot away. Note: A rod has a curved surface so that very little resounds back into the direction the noise came from making it even harder to detect.
From the article on human echolocation:
Vision and hearing are closely related in that they can process reflected waves of energy
Vision and hearing might not be redundant but they can somewhat substitute each other. So if humans collectively lose their eye-sight it is quite likely our anatomy will adopt to it in the long run by increasing our hearing capacity and range of perception. There are already ways in which "ear-sight" beats "eye-sight".
For example human echolocation allows us to perceive the density of an object. You don't get that information by looking how the light reflects from it! Although human echolocation might always lack in range compared to eye-sight it could definitely develop into something otherwise on par with normal vision or even superior.
Despite being less plausible than human echolocation – i.e. not proven vs. clearly proven – humans might be able to use magnetoception just like pigeons. However, to date studies remain inconclusive on whether or not humans have a magnetic sense. If they did not only civilizations could develop but also trading between cities far away from each other.
I have to admit though I can hardly imagine how weird people in this scenario will describe a travel route to a stranger:
"And when the road feels more going south listen for the hollow tree on the right and take the fork there."
The Tactile sense allows humans to perceive the surface condition and form of an object. You can also hold things with your hands to get the weight of an object – okay that's not your sense of touch but feeling the tension of your muscles but it's somewhat related.
Speaking to someone next to you: no-brainer. Long-distance communication might seem difficult at first but is not a problem after all. Whistled languages such as El Silbo / Silbo Gomero allow you to communicate with someone 5km / ~16,400ft away. If that doesn't suffice you still have braille. Now you might not be able to write on paper without building a type writer but clay tables will certainly work if your tech-level does not allow you to build the former.
Your fields will not vanish with your eye-sight! The same applies to orchards. In the past there were not only meadow orchards (German: Streuobstwiese) but also orchards combined with farmland (German: Streuobstacker). The latter cropping system will probably be most useful to and therefore establish itself in a world where all people are blind because you can use the trees as reference points to find the place where some specific crop grows. Cultivated plants will mostly consist of tubers and other unpretentious crops plus they can easily be stored or left underground if not needed – although you will lose more of them to rodents.
Why should blind people not be able to manufacture components and put them together to build a machine? The spatial imagination necessary to bring a complex machine like a computer to mind might seem impossible but maybe they will find methods to manage that. Just because we are so used to visualizing data doesn't mean we could not "auralize" data as well.
"Yes you were right: The x-ray scans hear like you broke your left ankle."
Admittedly, everybody suddenly losing eye-sight will be a horrible event. In the aftermath life will still be more dangerous than before for quite some time. However, in my honest opinion it is quite unlikely intelligent humans won't adapt.
Technology is the collection of techniques, methods or processes used in the production of goods or services or in the accomplishment of objectives, such as scientific investigation. -- Wikipedia
So yes, technology could exist. Maybe not in the form we have it today, but they will develop ways to do things better. For example, these people would probably develop a method of taming animals to help them "see." Likely they will still develop tools similar to what we have today. However many of the tools we have that affect aesthetics will not be developed. Why make an easel if you can't see the art?
The real question is "can humans survive and reproduce if all blind". If humanity can survive the blindness then they will continue what they always do, building culture, technology, and civilization. After all Blind people today still survive and contribute to society, expanding our technology and culture. being blind doesn't stop us from being humans, an amazingly adaptive creature that has a long history of using technology to compensate for our weakness. We are more deadly then creatures with teeth and claws, we survive and thrive in the most diverse and different environments, despite having no adaptations for them. Time and again our technology has proven better then other creature's adaptations. If we survive we will compensate for our lack of sight and thrive.
However, the question is if they could survive long enough to produce a culture and technology. This is a very different question then "can blind people survive in today culture." When most, or even some, people have sight it's possible for others to be blind while still surviving and thriving. Those with sight can do tasks that require sight, those without can do tasks that don't, and both can thrive and grow society by using those skills they are best at. However, if you remove all people with sight then you have no one to do skills that require sight at all, meaning blind individuals will have to do things that in modern society a blind person would simply pay someone else to do for them, or never try to do. You can't pay a taxi to drive you somewhere if everyone is just as blind on the road etc.
When the blindness first strikes were be in trouble. We couldn't hunt, we couldn't easily avoid those that would hunt us. We couldn't use a large amount of modern technology, like cars and standard computers. Many jobs constructing and repairing our technology would be MUCH harder, less safe, and possible impossible without extensive technological support to do when blind. We would adapt to address these concerns eventually, but if were all struck by blindness at once that's a much bigger problem. We would all be learning how to survive at once, and during that time when were adapting we would be so very very vulnerable. Lives will be lost, many many lives, during this translation where we have to re-learn how to provide for ourselves and build up the technology and infrastructure which does not require sight to use.
If all of humanity went blind today I think we could survive, we have tools we can repurpose quickly, and machines already do lots of the hard work for us. We would still suffer significant death toll at first, but we would survive. Once we survived one to two generations we would have modified our technology to be more convenient for blindness and be going well.
However, if blindness were to strike at an early time period humanity would suffer far more. We couldn't hunt, or effectively scavenge for meat while blind. We would be very easy prey to predators as well. If blindness struck when we were at the hunter/scavenger phase we would be in big trouble.
Our ability to grow crops, or pick fruit from existing plants, wouldn't be nearly as harmed though. Without modern technology we would have difficulty protecting our farms from anything inclined to take what they wanted, but we would have an advantage. Anything small enough to be after our food would be afraid of us due to our size, even if we wouldn't be good at finding them. Anything that would be big enough to hurt or kill us would likely have learned not to mess with humans, since at this point in time we would have been the apex predator. Eventually predators and other animals would 'learn' that humans were blind, but on a species level they wouldn't have evolved to realize this until long after we had time to adjust and create technology and techniques to survive without sight.
We also have domesticated animals, which would be a huge advantage. We could still use dogs to tend our sheep flocks to some degree without sight, and given time we could train them to better work for someone who is blind.
If we can survive one to two generations were be fine, and a culture and technology will still evolve as always. We will have used our brains and intellect to figure out how to work in a world that is completely blind and have a much higher survival rate once we have figured that out. In fact if we survive just the first few decades in any numbers were fine.
Since humanity is proven to be such adapters I would say we will survive, and eventually grow an extensive culture. However, if this happens pre stone age, or before we have agriculture or any technology of our own, we may not survive long enough to adapt.
If it affected a global population, maybe most people would not survive long-term, but a few would be in lucky situations. Maybe they found a niche like inside dark caves where they could compete, using their brains to set traps and predict prey behavior. Dark caves are not very rich environments for food, so you would have to embellish.
What if the global blindness did not only affect humans? Idea: a microbe that destroyed proteins used in vision. The same two (families) are used throughout all animals, though in different ways across major branches.
The cataclysmic event that you describe may create a society of blind people in the short term, event though as you describe, the event changes the genome of the species so that they will no longer be able to see based on light reception. So assuming that the survivors are still able to reproduce, I think if being able to see by light perception gives a selective advantage to the future generations then it is possible that it will become the dominant trait again. However, the dynamics of how this would play out is rather difficult to predict.
Theoretically speaking, many animals rely on other senses rather than sight, and it is not difficult to imagine that given time people might evolve to have more fine-tuned senses that compensate for this. If the selection pressures were such that based on this initial event the people who are able to adapt to living without being able to see (or people who are blind already) then we might expect them to become the dominant minority and so they could help to shape the future society to that which favours the blind.
Therefore I would conclude that due to selection pressures being less deterministic than we might think it is, the possibility of a civilization with mostly blind people (some would argue that this is already the case) is just as likely and possibly as one that is not.
I find it interesting to read this 2015 thread about the possibility of a blind civilization, and in November 2019 Apple introduces the mini-series called "See" based n that very concept.
While the mini-series is very entertaining, often intriguing, and sometimes peculiar, it does completely skip over the whole "farming, hunting, gathering of food" which as one person stated in the thread above would be vital.
