Yes, that's right, bloodline suppression!
Why was it so far-fetched for the pure human bloodline to have such a thing? After all, all the other races had it, so why should humans be left out?
Still, this was limited to certain rules, just like all forms of bloodline suppression. For one, there had to be a systematic bloodline inheritance for the race possessed by both parties. Most races that were young and new did not have bloodline inheritances of their own, such was the case for the current human race of Earth.
Older races had time to dig into the special nature of their genetics and develop them into abilities that worked on command.
For Dragons, this would be the ability to breathe fire and use magic. For Angels, this would be the ability to affect minds and wills. For Humans, it was Control.
