Here, eat this root
1000 A.D. That root is heathen and sinful. Here, say this prayer.
1850 A.D. That prayer is just superstition. Here, drink this potion.
1940 A.D. That potion is snake oil for rubes. Here, swallow this pill.
1985 A.D. Studies show that pill is ineffective. Here, take this antibiotic.
2000 A.D. Dude, that antibiotic is artificial. Here, eat this root.