You know what? I'm going to give the Doctor a pass on Za.
This episode, of course, contains the scene that pretty much everyone holds up as an example of how the Doctor, in his first appearance, was nothing like the heroic figure we've come to know and love. How back in his first story, he was actually willing to kill Za rather than have him slow up the group. This has become a defining moment of the Doctor's early character, so much so that Terrance Dicks had the Eighth Doctor come back to it in 'The Eight Doctors' pretty much solely so that he can realize what sort of man he shouldn't be.
But on watching it, I don't think it is a murder attempt. Or if it is one, it's a very badly staged one. As it happens on-screen, the Doctor reaches out and picks up Za's knife while everyone else is literally less than two feet away, in the middle of significant bustle. If the Doctor is planning to murder Za, his scheme is apparently that he's going to reach over, slit Za's throat with his own knife in the moment everyone's back is turned, and then...claim it was suicide? I might not credit the Doctor with much morality at this point in the show, but I at least assume he's got some common sense.
No, I honestly think his plan was nothing more than he said it was--to try to get Za to draw them a map so that if they have to waste time dragging his Cro-Magnon butt around, they can at least do so by the shortest route. His explanation sounds forced, but that's actually a more credible reaction. If he'd been guilty, he would have blustered and railed against the accusation. Knowing how stupid the truth sounded even as he said it would have produced exactly the same speech. So, Doctor? I'm going to assume the best of you.
Oh yes, and this was another great episode. The Old Woman is wonderful, with her fear played up as a threat to the group and then turning to their salvation, and Kal framing Za for her death. Again, I love the fact that these are not portrayed as stupid people. Their worldview is different, and their philosophy is far less genteel. But Kal and Za are both savvy, sharp men who improvise strategies and use their brains as well as their brawn to gain an advantage. I love that this is, when you strip away the furs and the scraggly hair and the missing teeth, a political thriller and a brilliantly made one to boot.