Evolving processes

At the moment I'm working on several different processes, relating to how a couple of systems will integrate and also Sox compliance for my project. Lots of the processes I see make me think "This system could only evolve, no one could imagine this from the ground up (without the assistance of lots of drugs)."

Take the financial markets for example, who the hell came up with futures markets? Derivatives ? Other stuff that the average person on the street can't understand? It all makes sense when you look at it one step at a time, but the idea of just going "Today I'll invent a mechanism for trade - lets call it currency. And while I'm at it I'll need to be able to trade expected future value of things based on option contracts."

The flip side of the coin is that, while complex yet sensible systems can evolve based on experience, not infrequently it seems we come up with ideas that just beg to have all involved in the process shot.

I guess I'm just split on the issue because I'm a fan of a green fields approach to pretty much any process I work on (after studying what was there before). Its probably based on the fact that I consider everyone who has previously worked on a process (including myself) to be an idiot until proven otherwise.