2000 B.C. – Here, eat this root

1000 A.D. – That root is heathen. Here, say this prayer.

1850 A.D. – That prayer is superstition. Here, drink this potion.

1940 A.D. – That potion is snake oil. Here, swallow this pill.

1985 A.D. – That pill is ineffective. Here, take this antibiotic.

2000 A.D. – That antibiotic doesn’t work anymore. Here, eat this root.