2000 BC – Here, eat this root.
1000 AD – That root is heathen. Here, say this prayer.
1850 – That prayer is superstitious. Here, drink this potion.
1920 – That potion is snake oil. Here, swallow this pill.
1945 – That pill is ineffective. Here, take this penicillin.
1955 – Ooops. Bugs mutated. Here, take this tetracycline.
1960-1999 – 39 more “Ooops”. Here, take this more powerful drug.
2000 – The bugs have won. Here, eat this root.
Source: British Medical Journal (author unknown)