50 Years of Doctor Who

a BBC 2013. Doctor Who chronicles the adventures of an extraterrestrial Time Lord from the planet Gallifrey. Although humanoid, the Doctor differs from you or me in many ways, not the least of which is the ability to navigate through space and time (using the TARDIS, an acronym for time and relative dimension in space, an erstwhile British police box). He also has two hearts and the capacity for regeneration when nearing death. This latter aspect of his species’ physiology has frequently been invoked as a plot device to introduce each new incarnation of the title character. Are there terrestrial species that might offer insight into the Doctor’s exceptional capacity for serial regeneration? In an