The way I see it. That ice age you're talking about may be the point where both civilizations splintered off. Ledo's civlization goes off to space while Amy's civilization stays on earth. There was a part where Amy's brother mentions a group of people who leave Earth after the ice started forming. So I'm guessing the people who left the planet took best and brightest of the civilization (such as scientists)because that was the best hope for continuing humanity. That might explain why Ledo's civilization is more advanced.
I agree with ya Acura, for that's what it looks like from what occurred in episode 2. it's a pretty good hypothesis for they are foraging things from the past instead of making any new technology, in the form of guns. They do have some advance technology like the mechs for certain activities. The main thing that interests me in this anime are the mechs. and the pirates having technology that surprises the main fleet.