Our language capabilities are evidently hard-wired but phylogenetically quite shallow and in the same way it seems  that there must be ego-instincts even more recently acquired. Most of our drives and desires, and the concomitant emotions go back much further into shared ancestry. The ego, however has little or no existence outside of desires, drives and emotions, so rather than being a new evolutionary gift it seems to represent an attempt at organisational unification of the diverse mental processes. Since it generally does a pretty bad job of this, at best creating excessive overheads, at worst giving rise to functional collapse, there must be other advantages it brings, probably along the lines of short-term gains in cunning and deception, a double-edged sword. Everything purposive is taken to be identification and so the ego as the origin of will is extended in time, as hope, regret, love and pride etc. Purposes are multiple and support or conflict with each other giving rise to complex emotions which as the epiphanies of ego are valued in themselves. Perhaps this hobbling attempt at unification is not just a bad turn in the free creation of life but an attempt to more fully inhabit a prior unity which has haunted the mind from its first self-conscious awakening.