sir_schwick said:
I think you caught onto something that is very important. Developement is about overcoming problems, not a histograph victory. This is why ages are not a good idea. They assume that all societies faced the exact same problems and figure out how to solve them the same way. A truly dynamic tech tree would focus on the issues caused by technology and developement, and what is avaliable to solve them. If you do not have Iron, why would you develop Iron working?
Enh. I think we're mixing up the idea of free research vs tech tree and the idea of ages vs none. While it's true that all societies didn't solve the same problems the same way (the Aztecs, for example, never discovered Iron Working, nor did they have horses for Horseback Riding), sooner or later you're going to run into things that *must* be researched in order to advance as a society. While China and the West didn't meet for most of history, they still discovered the same basic building principles (arches, etc). Wheels are a basic one, as is the creation of weapons and armies and systems of government. As societies grew, they developed advanced agriculture, road networks, etc.
Also, with trade, more and more of this becomes universal. A prime example is the Plains Indians of the American West. They became expert horse warriors after the horse was reintroduced to the continent.
While for the most part, research can be unfettered, you will eventually come to points where you can't have one advance without a previous one. There is no banking system, for example, without the basic concept of commerce to begin with, not to mention a road network, and every thing else that gets people to the point that they have enough extra resources that they can afford to put them into a bank in the first place.
And that's where ages come in. Ages tell you when you've passed one point of your existence (basic tribes, day to day survival, etc) and entered into another (actual city, standing army, record keeping, etc). While certainly in real life, no one sits down and says, "Aha! We are entering into a new age!", historians do look back and group human history into various ages. (Stone, Iron, Bronze, Information, Space, etc.) These ages are tied into technological and cultural developments (Bronze tools vs. Stone tools, for instance).
With a system of ages, historians (and players) can have an idea of where people are at at a given time. If I know a Civ is in the Stone Age still, I won't expect to see knights in shining armor charging me with a lance. If my Civ is starting to build railroad tracks, I know it's because I'm now having an Industrial Age.
At least, that's the difference as I see it.