2000 BC--Here, eat this root.
1000 AD--That root is heathen; here, say this prayer.
1700 AD--That prayer is superstition. Here, drink this potion.
1900 AD--That potion is snake oil. Here, swallow this pill.
1985 AD--That pill has become ineffective. Here, take this antibiotic.
2000 AD--That antibiotic doesn't work anymore. Here, eat this root.
