A piece of wisdom

I found this little piece of anonymous ‘urban’ wisdom today:
2000 BC  Here, eat this root.
AD 1000  That root is heathen.  Here, say this prayer.
AD 1850  Prayer is superstition. Here drink this potion.
AD 1940 That potion is snake oil. Here, swallow this pill.
AD 1985 That pill is ineffective.  Here, take this antibiotic.
AD 2000  That antibiotic is ineffective.  Here, take this root.
Makes you think.  (Like trees inside...)