I'd like to add my perspective as a struggling inventor. I can't speak to conditions 50k years ago, but a number of the challenges listed are still pretty relevant, and I've had to justify "why are things taking so long" to my friends and family enough times to pay close attention to this.<p>The big factors I see are: 'poverty trap', 'crude hacks', and 'full-time craftsman'. These interact. For example, most people need a day job. Even in R&D shops, day jobs are largely concerned with marginal improvements. I spent 12 years working as an R&D physicist, but I had to do my inventions on my own time because they weren't relevant to the incremental improvement products I was paid to develop. It's very hard to spend time working on a home run when your competition is hitting a thousand singles, and that is especially true with regards to possible uses of your time for paying the bills.<p>The craftsman thing is a big deal. I suck as a craftsman, mainly because I'm usually doing something for the first time. Need to weld it? Guess I'm learning how to weld. Need to polish it? Time to learn again. MATLAB is too slow? Hello C++. Oh, hey, now electronics are surface mount? Time to learn how to solder all over again. So, unless you are inventing something in a field you have specialized in as a craftsperson, everything you build kinda sucks. Then you have to figure out - is the problem with the idea or the implementation? Is there a different implementation which would be easier to build? What techniques do I have to learn to do that?<p>The workaround for this is to work with specialized craftspeople. Unfortunately, this adds different challenges. Now you have to pay them ('poverty trap') or convince them it's worthwhile (I didn't see 'social proof' on the list, but lets put it under value). Now you have to manage a project, which is a different skill set than inventing something in the first place. Sometimes, it's better going back to being your own craftsman.<p>In modern times, then you get to go to commercialization, which is the barrier which kills most inventions because the inventor rarely has the skills to do this right, and the people with the skills aren't usually incentivized properly to do it for them.<p>So, in short, I see the biggest problems for inventors not in the mental realm, but in the social. Inventors generally need help, and it is not until after the invention is a success that people see the value.