This one concept, I'm realizing, has ramifications across . . . I was about to say "our entire society". But I'd be wrong. Our entire world. Everything we do, from economics to warfare to romance, has been influenced by the fact that today's learning curve is orders of magnitude nastier than it was even a few hundred years ago . . . to say nothing of a millenia ago.
Now I'll explain.
Take a random middle ages peasant. He likely has a single job, that he starts when he gets up and ends when he goes to bed. He might be a farmer, or a blacksmith, or a musician (okay, not very likely, but possible). However, it's not hard to pick up a bit of the other professions. The basics of any one of those can be learned in a year . . . after that it's just practice. Somebody could be reasonably competent in any of those without needing much time.
Now take today. People spend ten years getting a degree just to get a start in their field, and are *always* racing to catch up with the current State of the Art. I've been programming for well over a decade, and I'm learning things constantly. There's no end. I've chosen backend as my specialty - I know nothing about CORBA, COM, MFC, or SOAP, and only bare scraps of XML. They're technically part of my profession, but I can't even learn my entire profession!
I'm not about to pick up metallurgy. I could spend another decade on that to begin with - I'd have to learn chemistry, and after that I don't even know enough to know what I don't know.
The learning curve has gotten absurd. A modern person can, if they're skilled, become an expert in a single *sub*profession. Not an entire profession, oh no - if anyone tells you they're an expert in "all parts of programming", laugh them out of the room. It can't be done. But I could, if I wanted, become an expert in user interfaces, or become an expert in algorithms (this is what I'm doing), or become an expert in networking.
I might pick up two of those subprofessions if I'm especially skilled.
Economics: someone trained in Profession A is going to require another decade of training to learn Profession B. If they're similar, it might only take a few years. Enormous inertia. If you're in a highly skilled profession, it's impossible to shift it to meet changing demand.
Warfare: imagine you capture the enemy supply depot, climb into their tank, and . . . don't recognize a single control. Sorry. You can't drive it. Now, if it was a chariot, it wouldn't be hard - horses have a pretty standardized interface. But you're out of luck - you can't capture their equipment anymore. There goes a good chunk of the Art of War.
Romance: If they don't know about what you're interested in, they're not gonna get interested - and they're never going to get to a level where you can talk about it as equals, because you're going to keep getting better at it. Give up and move on.
It's something I've been thinking about for a while.