Even If the World Ends, There Still Will Be a Ton of People Left
One of the things I find useful in thinking about life after a major, civilization-ending SHTF event, is historical population records. We can look at this Wikipedia page that details the history of population size in North America to get some interesting numbers.
The current US population stood at 325 million in 2017, so imagine if we had a catastrophe that wiped out 75% of the population. That would leave 81 million people on the continent, which is how many people there were in the US in about 1905. Albert Einstein was busy working on his theory of relativity that year, and New York, London, Paris, and all of the other major cities had long since been thriving metropolises. The Titanic sank just a few years later in 1912, and this is when the first season of Downton Abbey was set. So this isn’t exactly a reset back to savagery.
A much bigger catastrophe that cost us 90% of the population would take us back down to a population of 32.5 million, which would be the same size we were in the middle of the 1860’s. This decade saw the election of Abraham Lincoln and the Civil War. It was a bad time, for sure, but we had a large, thriving country with commerce, education, science, and many of the other things we associate with civilization.
Now let’s say that we lost a whopping 99% of the population, and went back down to 3.25 million people. That would bring us back to the mid 1780’s, or the time of the American Revolutionary War. At that point, Harvard University had already been in operation for over 150 years.
So sure, a 75%, 90%, or even 99% population die-off would be unbelievably catastrophic, but we wouldn’t necessarily go back to the stone age. There are a lot of people on this continent right now, and it’s getting more crowded by the day. One way to lok at all those people is as a distributed, highly redundant backup of the human race and civilization. With that in mind, there’s pretty much no chance you’d ever see anything like what most post-apocalyptic fiction portrays. In the very worst case scenario, it would look more like an episode of Downton Abbey or Redcoats, and not The Walking Dead.