Introduction
Few human experiences are as universal as identifying with a self. No rational analysis is necessary to perceive it. It is considered a self-evident truth. Yet, questions on the nature of the self and whether it even exists at all have fueled debates for centuries. The limits of the physical body are naturally chosen to demarcate what most call the self and the rest of nature. Not only do such practical definitions aid self-preservation, but they also form the functional unit of society. Both rational and sometimes irrational experiences, such as love, happen between and to individuals who are their distinct selves.
What seems utterly obvious becomes elusive under examination. If the body defines the self, does an individual losing their limbs lose themselves? At least partially? How about those who’ve had a stroke and can no longer communicate? Does a dependent newborn have less of a self than independent adults? When the independent adults lose their agency to dementia, does their self remain?
It would be wise to first look for the self within before looking for it in others. Little remains the same between being a teenager and raising one. Desires and disappointments could not be more different but the continuity of felt experience points toward an enduring self, yet the closer we look, the harder it is to locate. The question is not merely philosophical, it is existential. How we understand the self shapes how we see suffering and change. It influences how we deal with the ones who care for us and those who don’t.
Nearly two millenia before the scientific revolution, contemplatives in India approached these questions with unparalleled rigor. Before the scientific method, introspective discovery and discipled debates propelled curiosity about the self. The Buddha’s answer, anattā, represents a peak in intrsopective discovery. We move the wheel of understanding forward by tracing a path from the evolution of our brains, the cognitive spurts that made self-reflection possible, to an analysis of experience itself.
Evolutionary history of the self
The emergence of Homo erectus approximately 1.9 million years ago marked the first significant brain expansion in our lineage. Cranial capacity increased to ~900cc from ~600cc in Homo habilis. Much of this expansion occurred in motor cortex, prefrontal regions, and areas integrating planning with execution.
Walking on two feet freed the hands and elevated the head, expanding visual range for foraging efficiently across the savanna landscapes. Bipedalism could emerge from a refined autonmic nervous system that evolved through vertebrates to adapt to the changing environment. The autonomic nervous sytem and the endocrine systems thankfully do not need volutary control during a fight or flight.
Abstract thought emerged alongside the neural networks that optimized survival of the species. The most useful thoughts were naturaly selected.
But the feedback loop between upright posture, expanded foraging range, tool use, and brain development create a selection pressure for sophisticated motor-cognitive integration. H. erectus were the first hominins to leave Africa, to create Acheulean hand axes requiring complex sequential motor patterns, and likely the first obligate carnivores requiring coordinated hunting strategies. The complexity of neural networks not just brain size
The implication is profound: what we experience as consciousness – including the sense of a planning, contemplating self separate from mere bodily function – may be largely an epiphenomenon of motor planning circuits. The “self” that thinks itself a contemplative being arose from neural architecture built primarily for movement through space. Consciousness arrived as a late narrator to systems designed for motor execution.