A mutation/adaptation will normally be of benefit to the species, that is the whole point of the theory of evolution. If it is not a useful mutation and proves to be a disadvantage then it will not normally be passed on.
Who were these people who didn't read the bible 100 years ago? I'm pretty sure my Grandmother did and she was around 100 years ago.
Some people have a CCR5 gene that gives a natural resistance to HIV, it could well be that these people will more likely be the ones whos offspring are the future of the human race. Those without the gene will eventually die out. So I suppose this mutation of CCR5 is a good example of a very beneficial part of our evolution.
I'm not particularly interested in making moral judgements of how and why those who suffer from this virus contracted it.
I thnk you are blurring the difference between an adaptation and a mutation...many adaptations have been proved useful to a species (we will have a problem here is the term "species" means and has meant something differently to different people throughout time...what Evolutionary Biologists today call a "species" is not what Darwin meant when he used the term.
Also Gene "expression" is an important difference (though not at all a mutation)....when one set of humans has the CCR5 gene expressed and another set does not express that gene, yes those in whom CCR5 expresses will better survive the Aids epidemic (again this is correct natural selection), and if moms and dads from the same set mate then this will be reinforced (again adaptation/assimilation) but they will not because of this become a Hangrup or a Toldoid (a new creature)...it just assures their survival in this particular dilemma. So we are talking about expression of the CCR5 gene not the development of a previoously non-etant gene developed in response to a need or action. When HIV first was discovered these people with an expressed CCR5 already existed. In some cases they inherit the delta 32 variation which causes the receptor to act differently but this does not contribute to a new or different creature.
Now give us an example of an actual mutation...(the action of one thing mutating)...to mutate is to change or cause to change in form or nature. The CCR5 is not a change in form or nature of some other gene, the delta 32 version (and there are other variations) did not develop after HIV...