Just a silly thought, nothing I can really substantiate, but, consider the following. We as the audience and the characters aboard the TARDIS assume they materialize in the prehistory of Earth, when humans learn the skill for creating fire. But what if, just if, it was not Earth, but rather Skaro? What if the actions of Barbara, Ian, Susan and the Doctor inadvertantly cause a social rift among these early human(oids), one that leads to the eventual rise of the Thals and the Kaleds (or Dals if you're "old school")? Let's kick it up a notch. What if the caveman whom the Doctor was going to "brain" with the rock was the critical temporal nexus point? What if his survival set everything in motion? Ian's understandable act of compassion (staying the Doctor's hand) resulted in the creation of the worst scourge the universe ever experienced. Talk about a cosmic "Oh, crap!" Feel free the tear apart the idea. I'll admit it's not thought out too well. Just "fridge logic" speculation. Sincerely, Bill
The idea's been suggested: there's no proof that it's Earth in the Tribe of Gum episodes so it could be Skaro... could be Gallifrey! Either would be a nice irony...
No shame in being one of the great minds who think alike! Expanding your thought, the legend told in that first story suggests Dals/peaceful, Thals/warlike, so if the alien idea Ian introduced was mercy then it would be the Dals, and eventually Daleks, that he 'snowballed' into existence.
I've seen a theory floated that the planet in "The Tribe of Gum" is Mondas. I'd never considered Skaro as a possibility. As Green Lantern says, it could really be anywhere at all.
One advantage to it not being Earth, come to think of it, is that the supposed title 100,000BC makes no sense in terms of Earth's prehistory, but it could have been when Skaro or Mondas or wherever had their equivalent of stone age man. ;-)
Though later stories introduced the transduction barriers and that no time lord could travel into Gallifrey's past.
To my mind, Doctor Who is really about humanity, especially at that point in the series, when Ian and Barbara were the main characters. It's the perfect thing that the first place they travel - and the first thing the series shows us - is the dawn of their/our own species.
A good point, but the key aliens are warning echoes of humanity, so it's almost more universal to not know if those cavemen went on to become humans or Daleks or Cybermen or Time Lords, Trakens...