The traditional dates for Gautama Buddha's life are 563-483 BCE or 480-400 BCE, although according to Wikipedia:
Most historians in the early 20th century dated his lifetime as circa 563 BCE to 483 BCE. More recently his death is dated later, between 411 and 400 BCE, while at a symposium on this question held in 1988, the majority of those who presented definite opinions gave dates within 20 years either side of 400 BCE for the Buddha's death. These alternative chronologies, however, have not yet been accepted by all historians.
That leaves quite a large gap: about 150 years between the traditional and modern dates.
Is there no evidence of Buddhism being practiced in that period? Or is it the case that there was some such practice, but that it predates Gautama and was credited to him post hoc?