Hyperpolyglots are not born, and they are not made, but they are born to be made. There is a finite subset of the human population which has the right neurological equipment for learning and using lots of languages. That equipment may serve only a sub-component of language learning, such as mimicry, pattern recognition, or memory, or it serves those sub-components in a global fashion.
Those who become hyperpolyglots are those who meet two criteria. One, they are exposed to language material. Two, they undertake learning languages as a mission as well as acquiring the personal identity as a language learner.I describe the "neural tribe theory" of hyperpolyglots, arguing that they possess an atypical neurology that is selected by some environments and not others; presumably, there have always been humans walking around with that set of neurological traits or factors, only some of whom actually use those things for languages.
The globalized environment where speaking a lot of languages is rewarded and getting access to learning materials is easier. A talent for massive language learning has not been supported by the environment until very recently, so this is a phenomenon that is going to become more common and more visible.
