Hello Sangha...
An interesting quesion...

In fact, is our Buddhist practice an effort, in some way, to reverse or return to aspects of living that arose or were lost in those first days of our lives? Are we attempting to recover our original undivided state prior to "self/other" but --this time-- free of the greed, anger, fear, need and lack of understanding of the crying newborn? (That's Jundo's theory, which I propose.)
Ken Wilber, one of the utmost integrative thinkers in the US, suggests a model where development of human consciousness is illustrated neither as regressing or transcending, but as 'nesting', or integrating all previous developmental levels in to the new ones.

Imagine a developmental curve with beginning at the point A, with the top center of the curve at the point B, and the other point back to the starting level at the point C (a kind of a half-a-circle).

Point A is the newborn, or, arguably, sometime before, a baby well described by Jundo in the quote above. The baby's development includes development of an ego, or a sense of "I". All traditional western psychologies are concerned with this stage of maturation, which culminates at the point B, at the top center of the growth curve. At this point enter Transpersonal (beyond personal)theories of development. The ego is fully mature and able to transcend itself. Enter Buddhist psychology, with various techniques leading toward this objective, which is letting go of the ego, growing beyond it. All previous levels and awareness of them is not left behind, but included in the new levels of awareness. At the point C (enlightenment?) the person remembers all levels, but has grown beyond them, beyond any sense of duality or separation.

One of the big challenges facing spiritual teachers is to be able to recognize if the student is regressing (going backwards) or have progressed beyond the identification with the ego. One of the ways to recognize the difference is observe the motivation of the student in decision making (selfish or for benefit of others).

First there is chopping wood and carrying water, then enlightement, than back to chopping wood and carrying water. (donít remember where I saw itÖ)

With gassho