As you hopefully already know, our brains evolved from the inside out, so we have within us, the neurological structure of lesser creatures as they have emerged over time.
The Different Degrees of Awareness
Joshua Hehe

Interesting stuff, and I completely agree. It reminds me of Jason Brown’s three timescales, phylogenesis, ontogenesis, and microgenesis. Phylogenesis refers to development of species, ontogenesis to the development of the individual, and microgenesis to the development of specific brain states. To an extent, each timescale recapitulates the previous timescale. And in particular microgenesis recapitulates phylogenesis. So, successive brain states develop moment by moment in a series of overlapping waves, from phylogenetically oldest brain structures to phylogenetically newest brain structures, from brain stem through to cerebral cortex.

The flow from depth to surface is one of successive differentiation, so that brain state is most stable and most simple in the depths, and most transient and most complex at the surface.

Brown writes,

Waking objects are brief snapshots that dance over the glacial drifts of the core. (p. 60).

This is from his great book, The Self-embodying Mind.