Now, this brings up another question: What is man evolving into?
It's a good question. But it also suggests the idea that man is "highly" evolved, or is the "most highly evolved" creature. That isn't true in any evolutionary sense. There is no "more evolved" or "less evolved". Today's worms are as evolved as today's humans.
AIDS isn't airborne, but it could become so. If so, then we all may contract it. Some people, for some unknown reason, don't die when they get it. In short order, all the humans without this immunity would be dead. The only ones left will reproduce and their children will also be immune.
In that scenario, man is evolving into an AIDS-resistant version of today's man.
Humans screw up natural selection by fighting the selection'ing. We take care of other humans, even if they are unable to survive on their own. That's not a bad thing, don't get me wrong. But natural selection, if given the chance, would let our blind/lame/preemie babies die. We stop that, and so the genes behind those problems stay in our gene pool.
Again, I'm not saying we're screwing with the 'natural plan' by taking care of our less-healthy fellow-beings. There is no "plan" -- just a description of what happens if nobody intervenes. We intervene, so we aren't as susceptible to natural selection. (But in the case of a horrific plague, we'd be unable to intervene and natural selection would take over.)
Dave