How Can a Historical Approach Change Medicine?

How does a historical approach set light on how we understand science in medicine? I think one of the things that I've learned through study of the history of medicine is that there's nothing new under the sun. We can look back at the past and kind of thumb our nose and say, well, that's crazy that they used to do that or I would never do that. But then there's a lot of examples of similar behaviors today.