Continuing on with units from the game of Civilization, we come to the warrior. This, some might say, is more akin to representing the adventure party than the scout ... and yes, they serve more or less the same function. The scout enters a village and learns from it; the villagers offer the scout coin or technology of their own free will. The warrior, on the other hand, marches in and seizes it, while possibly destroying the inhabitants.
I find myself often considering elements of the game which seem to interest no one else ... in the historical sense, for instance, how did the classes derive? Obviously, there were not always paladins or illusionists; these things required advancements in technology both religious and educational (I've already written about how religion was a technology). Even the fighter has skills that obviously didn't exist prior to the existence of fashioned tools.
But then, I run the real world, and thus my world is fitted with a time of Neanderthals and Cro-Magnon man, these things not deriving from a magical impulse but rather magic itself being fashioned after effort and invention. Many fantasy worlds simply get around such issues by having the world - and the creatures in it - poofed into existence by magic and the gods, as neatly as the Bible does it. No need to worry about whether or not there were ever cavemen ... there clearly weren't, since man was conceived from the forehead of the DM.
This does bring up a case in point that some may not have grasped, that IF my world did derive from evolution (which I claim it has) and IF gods exist, which is necessary for clerics to have spells, then how does one reconcile the Biblical account of creation with word-of-God statement that I just made about evolution? How indeed?
I don't know, I suppose no one cares but me. I keep mysteries like that close to the chest, in the hopes that someday a party player might have a philosophical bent and might point out these little discrepancies ... and therein lies a most unusual adventure.
The warrior, then, is the result of a technological development. The difference between a proficiency and a non-proficiency results from a methodology of training. How is it the fighter has a d10 for hit points as opposed to a d8 or a d6? Training. Evaluation by a teacher followed by practice to harden, quicken and elasticize the body to make it swing the club so as to cause greater damage. Who improved the training so that four weapons could be learned, and no more than four lessons in the beginning, recognizing the efficiency of that number? How was the groundwork laid so that a level could be gained, and with levels multiple attacks? A steady, slow development of methodology.
In effect, then, the invention of the fighter class (surely the first class) was in turn the invention of the level itself. In my world, it is the ideal that hit points are a buffer between the combatant and the actual damage done by the weapon - that the hit points are the exhaustion experienced by the participant as the fight continues and as the combatant parries the enemy. My sword blocks your blow, so that you in effect 'miss' ... but the next time my sword blocks your blow, I feel the energy of your blow sweep down my arm and through my body. Even though your weapon doesn't touch my skin, I suffer 'damage' because the blow has helped exhaust me.
I recognize many people do not see hit points in this fashion.
Thus, I perceive your training as a fighter affects you this way. You begin with a certain number of hit points that result from your mass - a d8, say, if you weigh 160 lbs. As you train your way to first level, you begin to gain additional hit points that result from your fighter training. This takes years, but as you train, the instruction takes hold and you increase in hit points. Some, the instruction doesn't do very well, and you gain but 1 hit point beyond your mass (but you're still a 1st level fighter); others do better, gaining 4, 6 or 8. It depends on the individual. The player character is considered unusual, and starts with 10, the maximum. Constitution is added to this, and that is the result of training too.
Then, as you march your way through the wilderness, destroying monsters and villages (or whatever you're doing), you gain practical experience. As you do, there is a nagging in the back of your head, where things your instructors taught you just didn't, or couldn't, sink in until you got into the real world. You fight for awhile, and then one day you realize that you're dropping your sword every time you try to do this ... you realize how stupid that is, and you change your behavior. Suddenly, you're able to stop things from getting a handle on you, and overall you feel less exhausted with each combat. Congratulations, you've just gone up a level.
It begs the question, if the fighter comes into existence with the advancement of warrior training (circa 6-10 thousand years ago), when do the other classes emerge? The cleric seems obvious - with the discovery of meditation, of course. But where does the mage emerge. How early is the development of the thief (surely, very early). What technology produces the assassin, or the monk? Wouldn't the monk also be meditation?
The trick is to recognize that while the ability of the individual to swing a sword does not automatically equal the invention of the training necessary to swing the sword better, the presence of wealth that can be stolen does not automatically produce the thief. Nor does the process of killing in itself produce the assassin. It was necessary for an imaginative development to be made, that encouraged groups of people to do more than steal or praise or hit with the open hand - there had to be a motivation to STANDARDIZE the manner in which those things were done. Standardization resulted from hit-and-miss exploration, which in turn resulted in individuals discarding some techniques in favor of better techniques.
This is how development happens - when there's a joint recognition that a particular manner is obviously inefficient or impractical. This occurs even with D&D editions. A final 'right' answer will always emerge.
Sometimes, this takes a very, very long time.