I think its quite probable that this is an unanswerable question. The historical Buddha died approximately 483 BCE. The very earliest evidence of any sort of institutional activity related to him are the stone inscription edicts made by a "Indian" king named Ashoka who reined from 269 BCE to 232 BCE. That's hundreds of years of the early movement/religion that are completely dark to us and even these writings tell us nothing really much about the Buddha himself or his movement. There are Buddhist writings that describe the early sangha but its important to understand that these writings date from the 1st century CE so that's over 500 years of oral traditions before anything is put down in writing. Considering how unreliable hiagraphies are even when they are written by a teacher's own direct students we cant use the formal Buddhist scriptures as historical sources in my opinion.