I believe that Humans are a mutation of either the Earthen or the Troggs, who are mutations of the Earthen.

"and the drawves and gnomes evolved from earthen"

noone knows what the gnomes evolved from.

Gnomes evolved from Mountains giant of course :) (hey, they have four fingers hands too)

In a interview in early May with Tigole he mentioned the Vrykul are the progenitors on the human race similar to the Earthen.

As far as I can tell there are only four distinct lineages native to Azeroth as far as playable races go, the Elves, the Trolls, the Titanic races, and the Tauren.

To wit, Dwarves, Humans, Gnomes, and Troggs are all descended from Titanic origin.

The Trolls and Elves are distinct races and always have been, though there are Troll legends that say the Elves are an offshoot of them, though these are effectively propaganda.

And of course, the Draenei and Orcs are not native to Azeroth, neither are Ogres. Orcs and Ogres are native to Draenor, Draenei native to Argus.

Also, its important to note that anything to do with "Giants" is Titanic in origin, and anything to do with either elementals or azj-aqiri species (Qiraji and Nerubians respectively) are old god in descent.

magicswordsking: I always assumed that nelves descending from trolls who were altered by the Well of Eternity was highly likely, and that the nelves have gone to great lengths trying to cover up their origin out of shame of what their ancestors were.