2000 B.C. -- Here eat this root
1000 A.D. -- That root is heathen. Here, say this prayer.
1720 A.D. -- That prayer is superstition. Here, drink this potion.
1350 A.D. -- That potion is snake oil. Here, swallow this pill.
1975 A.D. -- That pill is ineffective. Here, take this antibiotic.
1998 A.D. -- That antibiotic isn't on your HMO formulary. Here, eat this oot.