This view of the world has been largely eroded among historians and lay-people informed enough to seek out the better kind of historical documentary*, but it's still a common enough belief, and it's alive and well in the worlds fantasy writers create. You have your civilised, sophisticated nations menaced by your primitive tribes. Nations have cities, tribes have settlements; natives have kings (if they're not republics), tribes have chiefs; nations have laws, tribes have customs; nations have religions, tribes have superstitious rituals.
But that's a gross oversimplification, caused partly by cultural bias and partly by misunderstanding about what's genuinely necessary for civilisation.
History is written by the winners, and so is the definition of civilisation. From Rome to the Conquistadors to the colonial powers of the 19th and 20th centuries, conquerors have essentially said "The definition of civilisation is anything exactly like us. These people aren't like us, so they can't be civilised."
Except that they also ignore or make excuses for all evidence to the contrary. A good example of this is the ruins of Great Zimbabwe (right) in the modern country of the same name. Until relatively recently, it was generally accepted that this must have been an Arabic outpost. There was absolutely no evidence to support the idea, except that "Africans couldn't build structures like this, therefore it couldn't have been African in origin."
Which, of course, is nonsense. There were highly developed ancient civilisations from the upper Nile to West Africa, not to mention the Egyptians, who were at least as much an African civilisation as a Mediterranean one. It's become increasingly clear that the civilisation who built Great Zimbabwe spread widely through south-eastern Africa, including a major Indian Ocean trading port, and was completely local in origin.
This process of marginalising other cultures has been repeated throughout the world, sometimes cynically and deliberately, sometimes from genuine lack of understanding about what is and isn't necessary for a society to be called a civilisation.
Fundamentally (and linguistically) civilisation means a society that's at least partly urbanised, and urbanisation has to start with a food surplus. A society that can afford to feed people not directly involved in food-production can begin producing specialists: artisans, traders, artists, soldiers, priests, nobility, royalty. Urban life also requires a level of organisation impossible under "tribal chiefs" or "tribal elders".
There have to be centres of concentrated population, but these don't have to look exactly like a modern city, or even the modern concept of an ancient city. There's a tendency to put an undue emphasis on stone or brick buildings, for the simple reason that they leave the most obvious remains. The traces left by wooden or mud structures are hard to detect, but these can actually be just as effective building techniques for their time and place and don't in any way indicate a "lower" level of society.
The way history has always been taught, for example, says that the "barbarian"** peoples of Gaul, Britain and Germany had no cities before the Romans "civilised" them, partly because the Romans said they didn't and partly because no impressive stone buildings have been found. What they did have were "hill-forts" like Maiden Castle (left) in Dorset. These are often thought of as purely defensive structures, but Maiden Castle, for instance, was an area of around 47 acres, surrounded by a palisade and earthworks containing within it homes, workshops and numerous other specialist buildings. It's believed to have been the seat of a powerful ruler who dominated the countryside all around.
In other words, a king in his city.
In much the same way, our comparisons of social institutions between traditionally civilised and traditionally uncivilised societies tend to be skewed by our preconceptions. Many cultures, for instance, believe that disease is caused by spirits or demons, and it's easy to smile at the naivety. Consider, though: they believe the cause of disease is invisible entities invading the body. So do we. They use the words spirt and demon, we use the words virus and bacteria, but they're all just labels put on things most of us have never actually seen.
Of course, I'm not implying these cultures have a sophisticated microbiology of their spirits and demons, and I'd certainly rather be in the hands of a modern hospital than of a shaman. Then again, I wouldn't be that thrilled about being treated by a western doctor from the 1950s, either. The point is that the assumptions we make about the relative value of beliefs are rarely disinterested.
Or take military forces. The Zulus who faced the British army in South Africa are often characterised as just a horde of warriors — of course, what else could African natives be? In fact, the Zulus had one of the best organised and disciplined armies in history, which developed out of a highly sophisticated civilisation. It just didn't look like a European civilisation or a European army.
Human civilisation is far more common than is often assumed. It's found all over Asia and Africa, and not just in the admitted-by-necessity areas. The Cambodian city of Angkor***, which flourished during the European middle ages, is now believed to have been as extensive as modern New York City, while pottery dating evidence suggests that civilisation may have arisen in West Africa even earlier than in its traditional cradle, the Middle East.
The Americas were full of civilisation. Everyone knows about the Aztecs, Maya and Incas, who are allowed the status of bizarre, barbaric civilisation, but they were the tip of the iceberg. There was a swathe of civilised cultures from Bolivia up to the Mississippi, rising and falling, interacting and replacing one another. The Mississippi culture, whose capital was in roughly the same location as St Louis, was one that took sophisticated archaeological techniques to find because it built in wood and earth rather than stone, but it had every hallmark of civilisation.
It wasn't the only one north of the Rio Grande. It's no accident that many of the Native peoples refer to themselves as nations. Many, such as the Iroquois, were anything but primitive in their organisation. I've also read that the east coast of what became the USA was not only heavily populated before the smallpox epidemic devastated it, but its people left many intact towns and villages, which the settlers merely moved into. I haven't been able to confirm this from an authoritative source, but I'd be intrigued to know more about it.
There are societies, of course, who fit the description of "tribes", and this isn't necessarily a bad thing. Cultural success, like evolutionary success, can involve either adapting the environment to your needs or adapting yourself to the environment. Many peoples have had no need for civilisation, because they're perfectly adapted to live in their surroundings.
Still, next time you're tempted to dismiss a culture as primitive because it's nothing like your own, try walking around and looking at it from all angles. You might be surprised how civilised it really is.
** The word barbarian is simply the anglicised version of the Greek word for foreigner, which didn't necessarily imply lack of civilisation. The Romans used it rather liberally considering that they, according to the original meaning, were barbarians themselves.
*** The best-known part of the city, the stunning temple of Angkor Wat, was only its centrepiece, like the Vatican within Rome.