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 doesn't work anymore. Here, eat this root!
