How Buddhism and Jainism started

(unknown source, please take it for what it is worth)

The spiritual master of the demons, Shukracharya, was arranging to bring amrita from heaven so that the demons would become immortal. In the meantime, Brhaspati, spiritual master of the demigods, took the form of Shukracharya and went to the asura-loka. The demons inquired, "Guru maharaja, have you brought us amrita?" He answered, "No, I met Lord shiva and he said it is not necessary. If you simply practice total ahimsa, you'll become so powerful that nobody can kill you. Lord Shiva sent two persons to teach this religion to you (the two persons were - one the Buddha, the other the Jain). And beware that the demigods will send a illusory form of myself to tell you this is all cheating and thus bewilder you."

So the two personalities started their training - they stopped the sacrifices of the demons and got them to practice ahimsa. Meanwhile the real Shukracharya returned, but was challenged by the guards, who refused to believe that he was genuine. Finally he found out that the demons believed him to have already returned and that there were two renunciates teaching ahimsa. He warned the demons, "Now you are finished. I am the real Shukracharya, and if you call the Asura-raja I can prove it. That other is an imposter. By following the ahimsa religion, you'll lose all strength. The demigods will surely attack you in the near future, seeing your weak condition." Though the demons finally believed him, by this time many of their number were staunch converts to the new religion. So their followers were mainly from the Asuric race.