Some other folks have already nailed it in this thread, regarding scientists being comfortable with change in the face of new evidence. Here's an example I like to use.... Remember when we were told that we should eat an ultra low-fat diet because fats cause cardiovascular disease? Then we were told that margarine (e.g. partially hydrogenated oil) was a much healthier substitute. Then, come to find out, margarine is substantially worse for you than virtually any other fat you can eat. Then we figured out that saturated fats were the most important culprit and that some unsaturated fats actually have some heart protective benefits. Interestingly, I never hear anyone say that they refuse to take their doctor's dietary advice because the doctors lied to us in the past.