Math vs. vampires: vampires lose

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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