2000 BC Here, eat this root.
1000 AD That root is heathen. Here, say this prayer.
1850 AD That prayer is superstition. Here, drink this potion.
1940 AD That potion is snake oil. Here, swallow this pill.
1985 AD That pill is ineffective. Here, take this antibiotic.
2000 AD That antibiotic doesn’t work anymore. Here, eat this root.
2009 AD Swine flu! Panic!
From How Isaac Newton Lost His Marbles (Drs. Jim Leavesley and George Biro), with obvious adaptations.

Alltop and humor-blogs.com both feel a little off. Originally published 2007.