While I don't think that any of the spoken/"human" races were created by the Allagans, that doesn't mean they weren't experimented on and the result of that experimentation was able to make a sub clan of one of the main races

Given the recent revelations, I believe that pure-blooded Garleans were the result of Allagan experimentation. Just like the Ixalion may have devolved into Ixals, proto-Garleans may have been different? Maybe their 3rd eye served a function? Though I dont know why not being able to use Magic can be an advantage.