The ego is not a biological concept. Neuroscience speaks instead of the "self-model," the default mode network, or motivation and reward systems. The word "ego" comes from psychology (Freud's "I"), and nothing allows it to be located in the brain.

The hummingbird. Its brain is tiny, yet it excels at spatial memory: it remembers where flowers are and the rhythm of their renewal. Its feeding choices rely on circuits of hunger, reward, and memory, which could be called a "food ego" by analogy.

Humans and other animals. Brain size does not settle the matter: some cetaceans have larger brains than ours. The number of cortical neurons is high in humans, but other species come close. The difference is probably one of degree (language, projection in time) rather than of kind.

Mutations and cell divisions. Mutations come from DNA copying errors, radiation, or chemical substances. Cell division follows a precise molecular cycle. No ego is involved, which you rightly leave to scientists.

Sound and light. Attentive listening to silence or to sounds, and fixing the gaze on a light (as in trataka), are studied for their effects on attention and emotional regulation. These studies describe measurable effects, not liberation in the spiritual sense.

Hinduism

Tradition distinguishes the Atman (the Self) from the ahamkara (the "I-maker"), present in all beings according to Sankhya. Creative energy is called Shakti. Sound is the creative Word (Shabda-Brahman, Bhartrihari; Om), and the yoga of sound (nada) listens to the inner sound. Tejas is the inner fire and light. Liberation (moksha) transcends the moral framework, which is only a preparation.

Buddhism

All beings are caught in thirst (tanha); human birth is rare and precious, for it allows for awakening.

The Buddha compared his doctrine to a raft: a means, not a morality to be venerated.

Sikhism

The Shabad (the Word) and the Naam are listened to inwardly; the divine light (jot) dwells within each being.

Judaism

The Zohar associates light (or) with divine emanation; Jewish prayer begins with listening: “Hear, O Israel” (Deuteronomy 6:4).

Christianity “In the beginning was the Word” (John 1:1), and “God is light” (1 John 1:5): the Word and the light, two gateways to the divine. Islam and Sufism “God is the light of the heavens and the earth” (Quran 24:35, the verse of light). sama, the spiritual listening of the Sufis, elevates the soul through sound.

The Soul and the Ego: Two Lights to Distinguish The soul is a receptacle of pure, creative energy. The ego is not the soul: it is the path the body traces to feed itself, the discreet principle that holds the chain of the living together. The hummingbird has its own, tiny perhaps, or immense for its size. No one knows where it resides, or whether it presides over the division of cells. Let us leave that field to those who probe it, and retain only this: many mistake it for the soul.

Does man bear the greatest ego on earth? Backed by intelligence, this ego gives him motives, desires, fears. It is not a fault to be punished, but a force to be purified, mastered, filtered, as one filters water before drinking it.

Then man can distinguish himself from the animal, not by morality, but by attention. Two doors open before him: listening and gazing. Shabda, the inner sound, which lets itself be heard when noise falls silent. Tejas, the light, which lets itself be seen when the eyes close.

Between this sound and this light, the ego ceases to be a master and becomes a servant again, and the soul at last recognizes itself for what it is: a space of pure, free energy.