It seems that this level must become actualized within an individual before they can enter into the next level, is this correct?
I think it will be useful to quote this for a moment.
(Sanskrit, prati, meaning "towards, for"; eka, the numeral "one") Those who achieve a certain measure of inner realization yet choose to follow the Spiral Path, taking untold aeons to complete their work. They are called "selfish" because they reject the Straight Path to Enlightenment, the Path of the Bodhisattva. Pratyeka-Buddhas attain enlightenment through the intellect and self-discipline. They lack the loving compassion and self-sacrifice of the Bodhisattvas.
"We must make a complete differentiation between the Sravakas and Pratyeka Buddhas on one side, and Bodhisattvas on the other. The Sravakas and Pratyeka-Buddhas preoccupy themselves only with their particular perfection, without caring a bit for this poor suffering humanity. Obviously, the Pratyeka Buddhas and Sravakas can never incarnate Christ. Only the Bodhisattvas who sacrifice themselves for humanity can incarnate Christ. The sacred title of Bodhisattva is legitimately attained only by those who have renounced all Nirvanic happiness for the love of this suffering humanity." - Samael Aun Weor, The Pistis Sophia Unveiled
As the intellectual humanoids emerge from the animal kingdoms, as they gain the gift of rationalization and the intellect, it appears that they become delusional and very damaging unto themselves as they attempt to utilize the intellect towards animal impulses. So am I correct in saying that the Śrāvakayāna path is one that can lead out out of delusional behaviors of self harm and towards ones' own individual perfection? And is it necessary to have this vehicle developed in order to move onwards to Mahāyāna and Vajrayana?