Groupthink and the inertia of ideas

This was posted to the cryptography mailing list as an example of how long it can take for experts to believe evidence.  Ulcers for years were thought of to be caused by stress (and many people still think so to this day) but are now known to be caused by bacteria Helicobacter pylori.  I just read about how if 40 years ago someone had even suggested that a condition such as ulcers was caused by an infection it would have been heresy.  However, they are finding even now that HPV is linked to cervical cancer and there could be other links between viruses/bacteria and other conditions. 

History of Ulcer Diagnosis and Treatment | CDC Ulcer

History of Ulcer Diagnosis and Treatment