trolls. trolls were first. at least, its hinted at heavily that they were at least the dominant force long before there was any human, elven, or tauren history.
as for tauren vs night elves....thats purposefully vague. tauren legend (which you can read in the druid training hut in thunder bluff, the stuff along the walls) says that the tauren or Shu'Halo as they are called in taurahe, were a product of the white stag and Mu'sha of the moon (An'she, her brother, is the sun). tauren legend says that Mu'Sha and An'she constantly chased one another across the sky, attempting to rejoin each other because they were lonely, and in her loneliness, Mu'sha found the white stag, a magnificent beast, and sought to court his love. my memory of the legend gets a bit fuzzy here (havent read it in awhile) but i think she snared him in the sky and his antlers tore holes in her net, creating the stars. eventually i think they gave birth to the tauren.
whos the white stag? some suggest cenarius. others suggest what the night elves call Elune, the moon goddess (but thats more in line with Mu'sha instead of the stag). in all likelihood, the night elves (and by extension, the high elves and blood elves, since all elves come from essentially the same "stock") probably came to druidism about the same time the tauren did. the night elves had a much more centralized society however, while the tauren were scattered on the plains of Kalimdor. it wasnt until Cairne united the tribes and led them to mulgore that the tauren became a cohesive unit as far as being a people was concerned. but for a good 15,000 years or so, the night elves pretty much had the run of things in terms of historical context.
