According to the Divyāvadāna, the Buddha himself instituted the drawing of the bhavacakra as a pedagogic device for the instruction of the non-literate in Buddhist truths. The earliest known example of the bhavacakra is a fresco (c.6th cent. CE) of Ajaṇṭā.
"Bhavacakra." The Concise Oxford Dictionary of World Religions. . Encyclopedia.com. (March 19, 2018). http://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/bhavacakra
"Bhavacakra." The Concise Oxford Dictionary of World Religions. . Retrieved March 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/bhavacakra