The royal cavalry may have been drawn exclusively from the ranks of the Patricians ("patricii"), the aristocracy of early Rome, which was purely hereditary, although some consider the supporting evidence tenuous.. Since the cavalry was probably a patrician preserve, it probably played a critical part in the overthrow of the monarchy. Indeed, Alfoldi suggests that the coup was carried out by the "Celeres" themselves. However, the patrician monopoly on the cavalry seems to have ended by around 400 BC, when the 12 "centuriae" of "equites" additional to the original 6 of regal origin were probably formed. Most likely patrician numbers were no longer sufficient to supply the ever-growing needs of the cavalry. It is widely agreed that the new "centuriae" were open to non-patricians, on the basis of a property rating.