"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 superstitious.  Here, drink this potion.
     
     1940 AD -   That potion is useless.  Here, swallow this pill.
     
     1985 AD -   That pill is ineffective.  Here, take this antibiotic.
     
     1997 AD -   That antibiotic is artificial.  Here, eat this root.