The brain of the normal human hasn't change structurally in what it can contain. What we choose to study, stress over, obsess  over, our nutrition or lack there of. Our Mindful practices shift our capacity and the pathways we use to process. 
In myself, I've access to the past life data that I've experienced. Plus I've worked opening vision and emerging pathways my whole life as the healer. It's what I came to do/be. 

So connecting to our older iterations, our genetic data, our essence of the living Divine - is all important. Some are asleep, some are napping, some are day dreaming, some are living in REM, some are waking, some are fully present and standing in the now, some are walking tomorrow and when clear, are acting as guides. Some yes, are many pieces, working in many planes at once.
But smart, a term to judge another.
Early humans, we didn't feel the need to be complicated. We still lived all the varied types of  existence.  

Not all are capable of waking in this life. 
The journey is ours.

Isn't the adventure amazing!