The Science is Never Settled.

The Science is Never Settled. If it’s settled. It ain’t science. For decades the “settled science” believed that stomach ulcers were caused by stress., This was so ingrained that, despite being proved wrong a while ago, many people still believe it. An unknown Australian doctor’ research convinced him they were caused by the h. Pylori bacteria. “The medical elite thought they knew what caused ulcers and stomach cancer. But they were wrong—and didn't want to hear otherwise.” Dr. Barry Marshall had to take the extreme step of infecting himself, then curing himself with antibiotics, to get the “settled science” changed.

http://discovermagazine.com/2010/mar/07-dr-drank-broth-gave-ulcer-solved-medical-mystery