Argentina has a very different genetic makeup from Mexico, Mexico is very mixed, almost everyone in Mexico possesses some indigenous blood. However Argentina's admixture levels are far below that of Mexico, its a possibility, but the levels in them is bordering on negligible. BTW i have Galician on my mother's side as well.
Actually yes. I do not think that the environmental factors played any role in the mutation of mammoth ancestors to develop fur. I do on the other hand believe that the mammoth ancestors who happened to develop fur due to random mutation were more likely to live to reproductive age in the cold environments. I'd wager that most if not all evolutionary biologists and geneticists would say the same. As far as your point about Martinez, Matthysse, and Angulo go I can't disagree with you. Are they pure "white"? No. But the definition of the word "white" is up for debate and if you consider someone with some indigenous blood and some white blood white then your definition is certainly valid. Most peoples' definition of the word white has become more and more liberal over the years. There was a time when Italians were not considered white and now they are almost universally considered white. The only thing I disagree with the is implication that South Americans who exhibits many Caucasian features are pure blooded Caucasian. It is highly unlikely that that is true. For example, Canelo Alvarez is as white in his features as you can get but there is no doubt that he has indigenous blood in him.
I get everything your saying, but just because something has not been proven to be true doesn't mean that its not true. Science has proven lately environmental changes have sped up evolution in some species in animals. Its a part of the theory of evolution that is up for debate, which I subscribe to, you don't, we can agree to disagree on that. Think viruses evolve by adjustig to the antibiotics that is attempting to kill them, quite quickly in terms of evolution, that is evolving to adjust to something in their enviroment. As far as South Americans go some are some aren't depends on the country and its racial makeup. Mexico Central America, Dom Rep, Puerto Rico, Colombia, Venezuela. Very diverse. Argentina, Brazil in places, Uruguay, parts of Chile not so much, so its plausible that large chunks of those populations are without any interbreeding. Similar in the U.S. we are very diverse, yet the vast majority is either White Black or Native American, depending on where you live determines how much mixed blood you have if any. I'm from Florida and you have no idea how many people can look at a Cuban who is whiter than they are and think they are a different race because they are from Cuba, most people are not that bright when it comes to stuff like this.