Borgfree,
I think I am remembering correctly, that it was scientists, who told us bacon was very bad for us, for some reasons, then it is not bad for us. Coffee was very bad for us then it wasn't. Milk, same thing, and many other food items and medicines, etc. I could be wrong but I do think it was scientists who were making those decisions.
This is so funny because this very subject was talked about in my psychology class a year ago. My proffessor was discussing how some people view scientists as "going back and forth about something" and the above example was given. He cleared things up by stating that, although scientists make mistakes, usually it is the media who reports on the findings that will blow it by using headlines that the scientist would never intend.
Also, think about your example. Do you really think this is a valid comparison? Do you really think that evolution is on that flimsy of grounds? You just cited a minor little matter when it comes to health and diet. Evolution is far, far more robust a theory than that. Although biologists disagree about the details (such as timing, exact mechanisms, phylogentic lineage) they are in near 100% agreement that evolution happens.
No offense, but you really, really need to investigate this much farther than you have.
Bradley