The largest religion on earth is not Christianity or Islam: it’s the widespread, faith-based belief system which holds that humans are separate from each other and from the world.
Humanity is becoming less religious as awareness expands that religions are nothing but a collection of unhelpful and unevidenced belief systems. In the same way, and for the same reason, humanity may one day do the same with the belief systems about self and separateness to which nearly everyone on earth is presently a devout adherent.
Upon close inspection there is nothing which tells us that self and separateness are real in any meaningful way. The human organism is inextricably interwoven with its environment, from which it must continually draw sustenance or perish. Science tells us that when you zoom in on the smallest and most fundamental components of matter it becomes clear that life isn’t happening at all in the way our mental stories describe it, and that what we normally think of as “objects” and separate “things” are more like loose relationships of particles and energy which have no clearly definable boundaries between where they end and the rest of the world begins. Neurology can’t point to any part of the human brain where a separate self could be said to reside.
Even in our own actual experience, self and separation are nowhere to be found.