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As the fiery tendrils of the celestial catastrophe engulfed the world, humanity found itself cast back to the primordial embrace of the Stone Age. The once towering achievements of civilization crumbled into dust, leaving survivors to navigate a world stripped of its technological marvels. In this new epoch, where the remnants of mankind struggled to eke out an existence, a daring expedition was conceived in the sun-scorched lands of Argentina. A ragtag crew, armed with little more than salvaged tools and an unyielding spirit, prepared to embark on a perilous voyage across the treacherous seas to scour the mysterious ice-clad wilderness of Antarctica and the riches entombed on the base therein. Their mission: to uncover forgotten secrets, salvage survival, and reclaim a semblance of the ingenuity that once defined their species. On the timeworn deck of a makeshift sailing ship, the brave explorers cast off into the unknown, setting forth on a journey that would either revive the flame of human innovation or be swallowed by the icy abyss of a desolate world.

I don't get this under estimation of humanity. If 99% of humans died, the planet became 3-5 degrees warmer, and all computers literally popped out of existence, we'd recover a ton of technology within a few centuries. We'd use a strange mish-mash of old and new tech, but people would write down a ton of information from the generations that remember the before times, and using previously learned principles, new generations would reverse engineer a ton of useful things.

Radio communications would be relatively easy to remake and will almost always exist in some form. A ton of useful developments like agricultural technologies and energy technologies would be too valuable to be lost for long. Gunpowder and firearms aren't going anywhere. All of these bedrock technologies would never totally disappear as they're too useful.

Even in a world constantly at war, these technologies would be essential to winning those fights. If you forget how to make guns, a group that didn't will conquer you. If you rediscover an old technology, it could give you an upper hand. If there isn't perpetual war, the risk of it and the benefits of trade will allow even more development and rediscovery.

The biggest reason for you underestimating humans is that you forget that most of our technology isn't physical. A boat may decay and become inoperable within a few decades, but the engineering principles that allow for the boat to function are unlikely to decay and fall out of disuse. Engines are useful. Boats are useful. Construction of high quality versions of these things won't happen overnight, but low quality and functional versions will get built.

People, even without writing, are exceptional at remembering useful ideas. With writing, we can store information outside of our minds and write out more complicated ideas than our working memory can handle. You think everyone is going to forget how to write mathematics? Hell no. We'll never lose written language, and that will allow us to find knowledge that no one alive remembers. The necessity of learning unknown concepts alone will ensure people would remember how modern languages are written.

The most impressive technology humans have is language, ideas, forms. Without forms, we'd never have built the most impressive physical structures and technology we have. Every advanced building began as a blueprint, and even Stonehenge required planning and communication. If every physical technology we've ever made disappeared at once, we'd rebuild many of those things by writing down what we remember and sharing knowledge with eachother.

TLDR: Ideas can outlive physical technology, and we'll never stop using useful tech in any apocalyptic situation. Only the Planet of the Apes neurological disease would stop humans permanently.