Andor said:
The world building thread got me to thinking.
In a world with a functional supernatural element, how big a difference do different food gathering strategies make in a clash of cultures? Or other technologies? Is a late Iron age druid more fearsome that a neolithic one? Is a psion/shepard at a disadvantage to a psion/farmer? Do some classes only become available at certain tech levels? Wizards would seem to need to come after the development of writing, for example. Do any classes go away with greater technology?
Put another way, if the native americans had been a bunch of druids, shamans, and rangers, would a bunch of european fighters, clerics and mages have had such an easy time with them?
This is a very complicated subject and there are no easy answers. I am an archaeology student specialized in Scandinavian pre-historic cultures.
The social structure often depends on the technological level of the culture. Most pre-bronze age cultures are gereontocracies. This is not absolute and is subject to error (there are great possibilities of error when looking at cultures that old and ethnological studies are not always good sources for looking at prehistoric cultures). This type of government cannot usually wield a large army. When in conflict, small units of warriors meet in a ritualised battle, that has few casuaties. Mainly a show of strength.
During the bronze age, it appears that a aristocracy emerges, with a few signs that notes that it might start in the late neolithic. These groups can wield greater groups of warriors and begin creating armies for conquest of other areas, thereby increasing their influence. These societies continue all the way to the middle ages, although they change in complexity and makeup continually.
The aristocracies also exist in the middle ages, but they are normally beholden to a king, who has complete power. This is a simplification, but does hold some truth. Some societies are different, but not much so. The basic makeup of the ruling bodies in the Roman Empire and the Greek city states does conform to the aforementioned, although they are much more complex. This is due to the pressure that the neighbouring cultures put on them and the requirements for wielding the massive amounts of trade that occured (not to say that there weren't much trade elsewhere but it was different, both in the ammounts and types of goods and in the reason why it happened).
This is one of the effects of a society's technology level.
The amount of work required to gather food also varies depending on how you gather it and what climate/terrain you occupy. Surprisingly, there is less work required for hunter/gatherer cultures to survive, than for agricultural societies. This is dependent of the aforementioned, but is true in most areas of habitation. Agricultural societies are often required to do alot of work to secure an output from their fields. Weeds have to be rooted out, birds scared away and animals has to be protected from predators.
This means the hunter/gatherer cultures often has more freetime than agricultural societies. That means that they have more time to improve skills that are not survival dependant. This is probably mostly social skills, due to the social structures in most such societies. Agricultural societies develope a wide variety of different skills to improve the outcome of their fields. Astronomy/astrology and engineering are some of those skills. This in turn leads to these elements transforming their cosmological/religious world. Often this is the time that cultures move towards more anthropomorphic gods rather than nature spirits (one does not necesarily rule out the other. There are alot of shamanic elements in norse mythology, for example).
Nomadic cultures can both subsize on hunter/gathering and herding. Both types probably requires an equal ammount of work, but herding has more security. These cultures are often very mobile and quite able to defend themselves.
What does this mean for a rpg? The more "primitive" cultures probably has more nature orientated classes, such as Druids, Rangers and Spirit Shamans. Bards are probably quite common as well. Nomadic groups are required to have great mobility. They often have the ride ability and does not carry more than absolutely needed. Agricultural cultures are more diverse. The new skills that comes with the neolithic package often opens up for more specialised classes, such as the Artificer. Specialised Fighters are still very rare in neolithic cultures, but becomes more common in later cultural levels. Druids are still quite common in comparison with Clerics, but this is slowly changing (depending on wether or not you allow Clerics to have shamanistic faiths).
I do not think Wizards should be used only in cultures with a written language. Iconography can replace a more standard alphabet as the magical writting in a spellbook. Magical symbols have a long history and could serve as the basis of the entire Wizardly tradition of a pre-literary culture.
Most spellcasters are very technology independent. It does not really matter much what kinds of non-magical technology that is available to a spellcaster, as it is the spellcasters spells that is the basis for his power. To Fighters, however, it is very important. The better the flintnapping techniques, the harder the metal, and so forth, the better.
Most classes do not become obsolete with increasing technological levels. It is different thing with social evolution. Rangers, Druids and like classes become alot more rare in more developed kingdoms/nations. The less wilderness the more rare wilderness orientated classes are (Druids and Spiritual Shamans could exist in urban settings, though in western oriented cultures, they are almost unknown).
EDIT: I mainly assume that magic is not very common. Perhaps just as much as our predecessors asumed, but i do not believe that technology would stop evolving because of magic. You have to have the touch of magic to use it, that is not the case with technology.
YOINK! 
