I may have been thinking about the ancient peoples of Europe, or even Neanderthals, at the time, but I realized one thing some virtual worlds lack today is the archaeological record found in the layers of sediment put down by time. There is no digital sediment there.
This was not always so, I don't believe, particularly with MUDs. In the non-virtual world space, with Google and the Wayback Machine, there is plenty of digital sediment. Wikipedia is all digital sediment. In MMOs, I don't think there is any, although I don't know every MMO in this manner -- in EverQuest II, if you stop paying for your house or guild hall, it's off-limits. Any "history" was put down by the game designers and isn't the same as the history of the digitally lived experience, even when that "history" refers to the original EverQuest.
In Second Life, you have to buy space. I am not entirely sure what happens with space that is given up -- I'm under the impression it gets sold, either to another user or a land broker, but either way the digital objects are usually wiped and something new is put in, with no layering on the past, just an erasing. Although it make digital building easier -- and I am a bit hesitant to call it "building" since it has very little to do with building in the physical sense -- it certainly does away with one of the usual conditions of the real world. I imagine if the owner of a zone doesn't want it, and can't sell it, it gets erased. Eventually Second Life will have to shrink, but I don't follow Second Life currently (it's creepy) and I doubt the Lindens will trumpet the loss of "land" like they trumpeted when all the corporations and embassies moved in (when the corporations moved out, it wasn't the Lindens talking about it).
MUDs, since many of them were non-commercial and run on some university server somewhere, just built up stuff over time. There weren't exactly layers, but there were additions and additions and more additions.
Some games use history as a feature. Dwarf Fortress is one; once you dig away the rock in the mountain, it's gone. Sure you can essentially fill it back in, but not with original stone, you have to make floors and walls instead. The history of the space is often there. SimCity, from what I recall, had some features that were easy to undo (like zoning) but other ones that weren't. Overall, though, you could re-build anything in-game, erasing everything before it.
But if we want to deal with virtual worlds as real-ish worlds, or as real worlds but in digital form, we need to remember what qualities digital worlds don't have. History is vitally important to us, but often the digital sediment of the past is missing. It's not presented as a bug, it's presented as a feature.
