Short answers, pulled from the story.
The word reincarnation derives from a Latin term meaning entering the flesh again, yet the concept appears in the Rigveda, Yajurveda and Upanishads of the late Vedic period between 1100 BCE and 500 BCE. These texts predate the Buddha and Mahavira and contain the earliest textual references to the idea of reincarnation.
Pherecydes of Syros flourished around 540 BCE and Pythagoras lived between 570 BCE and 495 BCE as the first famous exponent of the doctrine. Plato lived from 428/427 BCE to 348/347 BCE and presented accounts of reincarnation in works such as the Myth of Er and the Phaedrus.
Jain texts speak of a cycle of 8.4 million birth destinies in which souls find themselves again and again as they cycle within samsara. The four gatis include deva, demigods, humans, and hell beings, with nigodas existing as single-sensed souls at the bottom end of the existential hierarchy.
The Druze faith holds that the number of souls existing is finite and that a human soul will only transfer to a human body rather than any living creature. Reincarnations occur instantly at one's death and souls cannot be divided into different or separate parts.
Popular awareness of the idea of reincarnation was boosted by the Theosophical Society's dissemination of systematised and universalised Indian concepts during the early 20th century. By 1924 the subject could be satirised in popular children's books and had become a familiar element of Western popular culture.