The Evolution of Medicine

I have an earache ...

2000 BC - Here, eat this root.
1000 AD - That root is heathen.  Here, say this prayer.
1850 AD - That prayer is superstition.  Here, drink this potion.
1940 AD - That potion is snake oil.  Here, swallow this pill.
1985 AD - That pill is ineffective.  Here, take this antibiotic.
2000 AD - That antibiotic is artificial.  Here, eat this root.