Some of them had two distinct consciousnesses emerge due to their hemispheres no longer being able to communicate.

Arguably we all have more than one distinct consciousness due to both hemispheres being able to sustain one on their own, but generally aren’t conscious of it. And in case we are, interpretations tend to be religious as (generally, in currentyear) the right hemisphere consciousness is thought of as an other. As in, nope, that wasn’t your guardian angel, it was your right hemisphere violently pulling you out of your oh so comfortable left hemisphere tunnel vision to finally perceive some traffic instead of how hard your Lambo’s sound makes your dick.

Did you know that, evolutionarily, the interconnection of our hemispheres actually decreased with increased intelligence? Having drastically different takes on the world is very beneficial, likewise having them run concurrently: A wide angle lens for threat perception, a narrow angle lens to focus in on things. Iain McGilchrist has written two great books about the whole topic, but as a broad summary: The right hemisphere is the dominant one, having a holistic model of the world, while the left flourishes on detail and, if not in check, fabulates like a fisher – the right, as said, is supposed to direct its focus. Losing your left hemisphere is like losing your glasses, everything becomes fuzzy but you still know where you are, while losing your right is more like losing your eyes but being proud of how sharp your glasses make everything look. Symptomatically, you then see patients walking say through a door, noticing the hinge, getting drawn into it, really looking at it, and forgetting they were even walking. They’re stuck there, looking at the hinge. (That’s all modulo neuroplasticity, if damage occurs very early in life the brain can compensate). Excessive right-hemisphere dominance would be like dude, that’s all, you know, thoughts.