The original saṅgha split into the first early schools (commonly believed to be the Sthaviravādins and the Mahāsaṃghikas) a significant number of years after the death of Gautama Buddha; according to scholar Collett Cox "most scholars would agree that even though the roots of the earliest recognized groups predate Aśoka, their actual separation did not occur until after his death." Later, these first early schools split into further divisions such as the Sarvāstivādins and the Dharmaguptakas, and ended up numbering, traditionally, about 18 or 20 schools. In fact, there are several overlapping lists of 18 schools preserved in the Buddhist tradition, totalling about twice as many, though some may be alternative names. It is thought likely that the number is merely conventional.