Intriguing stuff, and some have also speculated that this might be harking back to the Doctor Who movie from 1996, where it's revealed that the Doctor is in fact half human on his mother's side. The reason for this in the film is his human aspects enable him to open the Eye of Harmony, the power source of the TARDIS.. It might also explain the Doctor's predilection with Earth.
Paul McGann played the Eighth Doctor in the movie taking over from the incumbent Sylvester McCoy. He started the' Doctor kissing his companions thing', which I've never liked. He's an alien isn't he!
Although, he continued to portray the Doctor in many audio adventures, he did return to TV screens in the prequel mini-sode, The Night of The Doctor, which aired prior to the fiftieth anniversary episode, Day of The Doctor.
The Night of The Doctor served to tell the audience that the Timelords, following the Timewar were as much hated as the dreaded Daleks. We also see the Doctor's regeneration into the War Doctor, with some help from The Sisterhood of Karn.
Is this reminder that the Eighth Doctor's half human aspect is a hint of what's to be revealed at the climax of this season? (most fans chose to ignore this part of the Doctor's personality, believing it to be simply a mistake in the writing).
Coincidently, this is the latest Eaglemoss figure of Paul McGann as The Eighth Doctor.
Later on tonight, when the latest episode Hell Bent airs we should know for sure, or not depending on how convoluted the story gets.