The Long Way Back to Ourselves

5.1

Epidemics, Part One: The Price of Density

This episode shows why fast-spreading diseases such as measles and smallpox are not something civilization suffers from outside but one of its own products. It draws on physician Peter Ludvig Panum's 1846 report from the Faroe Islands, where he recorded a 13-to-14-day measles incubation period and found only survivors of the 1781 outbreak, 65 years earlier, remained immune. You get statistician Maurice Bartlett's threshold of roughly 250,000 to 500,000 connected people, below which measles dies out for lack of hosts. The episode corrects the textbook claim humans caught tuberculosis from cattle, citing genetic evidence it may have run the other way, and covers the 1377 Ragusa quarantine rules, which worked despite a wrong theory of contagion.