Does it just spontaneously appear?
It is often posited that human consciousness arises from the complexity of our brain processes. That it somehow emerges, spontaneously, when a sufficiently complex interconnection — one involving feedback loops, for instance — of data-processing modules takes place.
From such a hypothesis it follows that within a similarly structured computer program some level of consciousness may well emerge — not as a result of deliberately designing or programming it, but spontaneously, simply as a consequence of the complexity of the program (provided that such complexity is of a certain level and of a certain kind).
It seems to me that such theorizing about the emergence of consciousness is completely misguided. A crucial point is that our consciousness is highly limited. We are completely unaware of all kinds of processes constantly taking place in our brain. And the workings of the processes of which we think we’re aware still remain, to a significant degree, hidden from us. We tend to construct narratives and rationalizations (often unconsciously) that provide a coherent view of our actions, even when what really prompted those actions is unknown to us.
Thus, if consciousness were simply something that naturally emerges from biological (or artificial) neural networks of a given complexity, one would have to explain why we are aware of certain brain processes and not others.
It seems far more plausible that consciousness (including self-awareness), has been precisely “designed” by evolution to work the way it does. It is present when it is advantageous for our Darwinian fitness, and absent otherwise.
Consciousness should be viewed as just any other body organ, fine-tuned by evolution to serve a particular purpose, like an elephant’s trunk, say. Or just like the pleasure we experience when we eat or when we engage in sex: neither less nor more than strictly necessary to optimize our evolutionary fitness; exactly calibrated to meet certain specific goals.
And even in the exceedingly unlikely event that “advanced” consciousness had somehow emerged spontaneously, like an evolutionary byproduct (a biological spandrel¹), its impact on human behavior would have been so consequential, that it would have been immediately subject to being sculpted — constrained here, heightened there; made to be activated or dimmed under these or those circumstances — by natural selection to eventually become like any other trait resulting from this evolutionary mechanism.
It’s far more likely that some incipient form of consciousness arose at some point — probably something very basic related to sensory perception — and then natural selection progressively worked on it. We wouldn’t expect a fully formed eye to suddenly appear in evolution; rather, eyes gradually emerged from their earliest predecessors: simple photoreceptors that sensed light. We should apply the same logic to the evolution of consciousness.
¹ In evolutionary biology, a spandrel is a phenotypic characteristic that is a byproduct of the evolution of some other characteristic, rather than a direct product of adaptive selection. That is, it is a trait that is not particularly advantageous to have, though it is retained because it is not particularly harmful to have.
The term “spandrel” originated as an architectural word for the roughly triangular space between the tops of two adjacent arches and the ceiling. These spaces were not actually utilized until later on, when artists realized they could make designs and paint in these small areas, enhancing the overall design of the building.