I have always felt that the first age was the one represented by the lava, given how it's populated primarily by dinosaurs. The next era is likely the one represented by desert given the look of the buildings, followed by the forests and the craggy highlands, with the survivors resembling people that are vaguely Victorian. The next era is the one represented by the towns with the very contemporary design of the buildings, followed by the ice age/thaw, with the ultra modern buildings and the skelebots. The last era is that of the skelebot graveyard which represents an era in which humanity has gone extinct and the only thing left were the skelebots. Does any else have thoughts on the matter?