Re: thoughts on Antarctica
Antarctica was south east of Africa and south west of Australia. Of course this was 225 million years ago and man didn't appear until 150,000 years ago. So there was a pretty good distance between the southern tip of Africa and Antarctica. But even if it was inhabitable at some time during the existence of man and for some reason, man decided to just head south on the hope that they might find something, they would eventually be wiped out. The continent was continually moving south and it would eventually be too harsh for anyone to survive.
Re: North American Indians
I don't really know what I'm talking about here, but I've developed a theory on what you have said.
the plains Indians [are]... more advanced.
I'm going to assume this to be true.
So the general theory of man's migration to the Americas is that they came across the land bridge that connected Russia to Alaska. On the journey south, it looks like some people decided to stop travelling and settle. The Incas and the Aztecs continued moving. Perhaps they thought that if they kept moving south that the climate would keep getting warmer and more pleasant, so they continue south. And perhaps the plains Indians are just content where they are and decide to stay.
The Aztecs and the Incas settle far to the south, near the equator (if I can accurately remember my history from eleventh grade). The life that they start is pleasant. There is a warm climate which temperature fluctuates little. Fertile soil for agriculture (if they've discovered agriculture). It rains often so they have fresh water, etc. etc.
The plains Indians don't have it so 'easy.' The temperature fluctuates in throughout the year. They have hot summers and cold winters. Everything dies in the winter. So they have to find a way to get through it. They develop methods to make it through the winter. They have to use their outside resources and their brains to insure their survival.
That's the best I can do. Sorry to pretend to know what I'm talking about. Were they indigenous people? Did they have agriculture? I guess I could have done some research before writing this. But I've already written it...and now I'm posting it.