Hi Gary,
It seems to me that around the time the game Civilization begins, 4000 BC, the Earth was fairly spotted with tens of thousands of clans or groups of people. They didn't start out in cities and then spread around the countryside. Rather they started in the countryside and eventually migrated or clustered or perhaps coagulated into city-states. The city-states eventually banded together to form countries or civilizations or regions or whatnot.
I concur with your thought. The way it is in the civ games is primarily a game mechanic decision. However:
But it wasn't like anyone started with Babylon and then set out to discover or found new cities. Was it?
Well, in case of Babylon certainly not. They were just one of many cities that were founded just as you described above. Babylon is not even close to being the oldest city there, that honor probably goes to Uruk and Nippur, according to Marc Van De Mierop, "A History of the Ancient Near East", Blackwell Publishing, Second Edition, 2007. Babylon just happens to be the capital city of Hammurabi, who was one of the most successfull warlords of that region and time and unified a large area through conquest and betrayal of his former allies.
But in case of, for example, the Greeks the answer is "Yes, yes it was." The Greeks founded cities all over the Mediterranean, just like Civ represents it. Since the Greeks are at the root of the European flavor of civilization and Civ is an eurocentric game (meant as a neutral observation), the settler mechanic has historical significance. Some millenia before 1492 AD.
There are other inaccuracies that I personally find much more off, just two points off the top of my head:
1. Civ is extremely dependent on land. The more land you have, the more population you can sustain, the more shields and trade you get, and the more powerful you get. While this is a very good and very satisfying game mechanic, it is also highly unrealistic. In reality, for the majority of countries, the majority of economy, industry, wealth, population and any other aspects that contribute to their power are concentrated on a small percentage of their territory. If you wanted to simulate this in a civ game, you had to make most cities of a civ comparably poor in most aspects, and a very few cities big super cities. Especially in Civ3 however, you can and probably will distribute your power fairly even throughout your empire, with little exceptions like stronger super science cities or weaker edge cities in unhospitable terrain.
Look at the sizes of the countries who participated in WW1 or WW2. In Wikipeadia there are very nice color-coded maps. Basically, the whole world is colored in one color, the color of the allies or Entente, and tiny flecks of land are colored differently, axis or middle powers. Now, you could say "No wonder they lost the war, as small as they were", but that misses the point completely. In fact especially Germany was very powerful in relation for their small territory (in comparison to the USSR, the French and British World empires, or the US). That worked, because in reality, other than in Civ, territory is not a prime requisite for power. High industrialization, high technology level, excellent infrastructure, a tedious workforce and national hybris are.
2. Cities are all self-sustaining on food. This is again a very good and satisfying game mechanic, but, again, highly unrealistic. Even in the antiquity food was shipped long distances. Athens gained their grain from the Black Sea coast, Rome from their colony "Africa" (today Tunesia), later from Egypt. Today, food is traded on the world market and large shipments of food will be shipped around half the globe.
What vxma said is absolutely correct. That is also the reason I would not introduce Civ in school, except perhaps for certain scenarios or under the premise to look at what Civ does and to contrast it with reality.
I also heartily agree with Buttercup in all points, especially the lack of internal struggle. Rhye's and Fall (for Civ4) has a nice idea about stability, which is, however, a bit too random for my taste, but is going into the right direction.
One last point, about population: The FIRST population point of a city represents 10,000. They then increase. And no, a Swordman unit does certainly not represent 10,000 people for a grand total of 300,000 men for 30 Swordmen in an ancient army. Firstly, the game does not suggest any of this: A city does not shrink in size if you build a Swordman unit, so they certainly do not recruit a full population point. Secondly, these gigantic numbers have no base in reality. Ancient armies seldom had more than some tens of thousand soldiers. Which is still a gigantic mass of people regarding the much smaller world population and lower technology regarding logistics (like food you have to grow and carry around!). And don't take numbers from historical texts too literally: Historians will tell you that exaggerating the size of armies was a kind of art for historical historians.
Lamabreeder