That game exists and is called Wurm, something the Minecraft dev did with a friend before he left preferring faster paced Minecraft game of 3-D blocks over Wurms slower skill based game based on 2.5D terrain.
http://wurmonline.com/Development continued as beta for years and they just did 1.0 release a few months ago that had upgraded customized PC and animated mob models.
Everything in the game beyond the environment is made by PCs using skills that take years to master. You do not start in an fig leaf, you get a peasant tunic for modesty. You also get a set of wooden noob survival tools that respawn with you, unless you choose to drop them and forage stone and sticks to make your own tools and fire.
Mobs are hostile, many noobs make the mistake of thinking collect ten rat/wolf pelts is the first thing they can do like any RPG game, but that quest does not exist, and wolfs/rats will kill you for a long time. Even if you can defeat those you have to watch out for huge lurking spiders/trolls hiding in the woods.
It also has health, thirst, nutrition, hunger and rest.
The elevation map itself can be edited using a shovel to dig/drop dirt and hatchet/sickle to cut/plant trees bushes, or put in roads and farms (roads are simply textured tiles, not vectored deformations). Of course older servers are more developed, and have neighbor conflicts, but newer servers come out as population grows, the PVE servers have become more popular than PVP in recent years.
Wurm would benefit greatly from Outerra, the dev environment is similar API of OpenGL/AL with Collada models. The distant lands are simply textured elevation maps, basically what Outerra starts with, which is not very immerssive. It uses animated sprites for grass, planned to be switched to geometric shaders.
The main difference I see is algorithmically instanced trees vs. individually plantable/destructible trees, which Outerra has said is in the works. The cool thing about all flora is they are living with each trees, bush and grass all having different growth stages & spread algorithms. Time flow is 8x with seasons. The only game I have ever played where you can actually be a forester that can change the forest.
The terrain model uses ocean connected isles (servers) of 2kx2k or even 4kx4k tiles, where tiles are probably 2mx2m. So smaller and more detailed than earth, but all of the isles could be put on the same world if dynamically loaded like Outerra does for earth.
The only problem with the survival game is that phase does not last long, the newest server was restricted to new characters only for this reason to slow down development. WIth metagaming forums and chats it is otherwise too easy to yell looking for village to meet the man giving you tools, food and a warm bed. So the world cannot truly develop starting with the stone age simply because it is a MMO and different people have different play times and lengths, there will always be someone with more time and thus more skill. Just like humanity skilling is an open tree, since it takes so long the main limit is time just like real life, so people tend to focus.
One possible way around this could be a multiverse where the same base terrain has different characters of different epochs all with different layers of terraforming, buildings, roads. Then you just port to the epoch you prefer, from stone age to medieval to industrial.