Joshua Dyal said:
Anthropologists will tell you that before Homo sapiens sapiens rose to the fore and the other human(oid) species went extinct, there were probably half a dozen humanoid species or subspecies in Africa alone. I'd guess the races from a typical D&D campaign aren't much more than sub-species apart from each other. After all, half-orcs and half-elves, at least, can create viable, fertile offspring.
that's a good point, but that can also be used to argue the other way.

you don't see too many of those other hominid species walking down the street today -- because competition between the hominids resulted in our species coming to dominate the world and we drove all the rest extinct. i'd suspect the same things would happen in a typical fantasy world also, so i'd still maintain that a world with dozens of advanced, civilized, sentient species is a bit far-fetched, unless you are not using evolution and other real world processes to describe how the races arose and developed.
Lord Ben said:
In D&D you have dozens of races competing for space and dominance. In our history you had dozen's of Kingdoms and nations? Why is it so hard to believe there would be dozens of races competing with each other when in our history there have been dozen's of nations in Europe alone that have all competed at one time or another.
apples and oranges. firstly, by having so many sentient races, each having, say, only one small kingdom, you are giving them too small a population base and gene pool to survive and grow. it's different from our world where we're all humans capable of breeding with each other. if you use the standard fantasy convention that different races
can interbreed, after a sufficient period of time, the majority of the population should be halfbreeds, and there would be very few pure-blooded individuals left.
aside from using logic and scientific arguments into the merits of having a few or many humanoid races, there's a good thematic reason why they should be limited.
most fantasy worlds with a lot of different races tend to give each race a stereotypical personality and culture. this is rather unrealistic and it pigeonholes the race into being a "one-trick pony." there's a couple of dragonlance threads already floating around here about how a lot of people dislike the presentation of the "little" races (dwarves, gnomes, and kender) in that setting because they are so cliched.
on the other hand, if you allow each race to have the same diversity and range of personalities and cultures that humans always seem to have, you begin to lose the differences between them. and if there's no real difference between the races besides a few game stats, you might as well consolidate them into a smaller number of races.
so instead of having orcs be the "barbaric humanoids," hobgoblins being the "civilized, regimented humanoids," and goblins being the "small, cunning humanoids," why not just have one race with three different cultures? is there really a need to define a new species for each permutation of personality and culture?
of course, there can always be compelling in-game reasons for having a plethora of species (perhaps the gods created them all purposefully). but i think serious consideration should be made about the role and purpose of all the races in a campaign world.