2000 BC: Here eat the root, 1000 AD: That root is heathen! Here say this prayer. 1865 AD: That prayer is superstition! Here, drink this potion. 1935 AD: That potion is snake oil! Here, swallow this pill. 1975 AD: That pill is ineffective! Here take this antibiotic. 2000 AD: That antibiotic is poison! Here, eat this root.