Efthimiou supposed that the first vampire arose Jan. 1, 1600, around the beginning of a century during which some of the first important modern writings on vampires appeared. The researchers estimated the global population at that time, based on historical records, as 537 million.
Assuming that the vampire fed once a month and the victim turned into a vampire, there would be two vampires on Feb. 1, four the next month, and eight the month after that. All humans would be vampires within 2½ years. –Math vs. vampires: vampires lose (World Science)
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