I don't really want to get involved in this discussion, but I would like to get some things off my chest.
Please...I beg you...everyone, stop with the lame response "it takes a really long time". You all know this is an unacceptable response. Imagine if physicist said "we know the speed of light is finite but we can't figure out what it is cause it's just so damn fast". Please, there is nothing wrong with not knowing, just admit it, scientist do it all the time.

DA Morgan, AIDS does not evolve, it adapts. Evolution necessitates speciation.

Furthermore, I just can't ignore the fact that several thousand generations of fruit flys have yet to produce a single advantageous mutation.
?It is a striking, but not much mentioned fact that, though geneticists have been breeding fruit-flies for sixty years or more in labs all round the world?flies which produce a new generation every eleven days?they have never yet seen the emergence of a new species or even a new enzyme.? Gordon Rattray Taylor (former Chief Science Advisor, BBC Television), The Great Evolution Mystery (New York: Harper & Row, 1983), p. 48.

On a lighter but still baffling note. I find that pork challenges evolutionary theory. How could an animal evolve to be tastier. wink