system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If modern humans have been around for hundreds of thousands of years, why have we only discovered tools/tech/civilization as we know it relatively recently in that scope of time?
gpt
Technology builds on top of itself.  Think about how much we can do now that we have computers that would have been simply impossible to do prior, no matter how smart we were.  Really, though, it seems that the big leap forward occurred when we invented the written word (although there could be some confirmation bias here because we, by definition, have no history from prior to the invention of writing).  Prior to that, someone comes up with a brilliant idea, they try to explain it to other people, who doesn't understand it as well, and when he dies that knowledge is effectively lost (or only preserved in a limited corrupted form).  Once you can write things down you can store them for longer periods of time, and you can copy and transport them to further geographic locations.  This allows knowledge to be shared with people that aren't from the same time and place as each other, which allows people to build on others prior work.