...living in close quarters with animals forced divergent evolution between the South American humans and the European humans: the former differentiated against microbes and animal-borne diseases and the latter against parasites.
I think we are arguing semantics here. I am not arguing that the human species has not evolved at all in the last 200,000 years. I just mean that the rate at which our species was moving to a new species slowed to a crawl or even stop.
However, you can argue until you are hoarse about what exactly are the mechanisms of evolution and what counts as a mechanism and what doesn't. For example, you might argue that the constant immunological reaction to constantly evolving pathogens pushes our species in a new evolutionary direction...but then can you not argue that vaccinations do the same thing? And since vaccinations are a human-produced pathogen resistance mechanism, then does all pathogen resistance become evolution, or does none of it...or just the stuff that happens outside of human control?
But then that leads to another problem of what is considered human-caused pathogen resistance: is my body resistant to several forms of e. Coli becuase I lived and grew up exposed to e. Coli in my processed food? I very possibly would have been exposed to e. Coli if I lived a wild life 200,000 years ago, but not as easily as I have been thanks to food that was insufficiently cooked. So is e. Coli resistance evolution, or human self-modification?
And is human self-modification evolution? If so, where do you draw the line? One nasty biproduct of human society is constantly evolving and aggressively-spreading forms of influenza, like the current swine flu epidemic evolution? It wouldn't have happened at all if there were low density human populations as there used to be.
Because of the complexity of the thing, I tend to discount all immunological changes the body makes as non-evolutionary. For example, dinosaurs huge size was owed to high concentrations of oxygen in the air, and a food chain that was buoyed by it.
Typically, one argues that evolution occurs as a species moves into a newly created ecological niche, or as a creature is forced to evolve to survive the closing of a niche. These are typically not products of bacteria or viruses, but rather higher level changes in the Earth.
Now, you could argue that a bacteria will rapidly evolve its DNA to be drug resistant. You could say "the bacteria with the resistant DNA live, and the species of bacteria has evolved." In essence this is true, but once again, the evolution of that bacteria has been forced upon it by human society.
And for all intents and purposes, all the changes in the human race since 198,000 B.C. have been minor and unexceptional. My argument was mostly that nothing in the last 200,000 has made our IQ's any higher.