The following notes are insights compiled from the book _Consciousness Demystified_ by Todd E. Feinberg and Jon M. Mallet. Before diving into evolution of consciousness, consider reading [[What is consciousness?]] for an introduction. #### Stages of consciousness When it comes to evolution, nothing pops out fully built out of vacuum. There's a smooth continuum in how complex features appear. Consciousness is certainly a complex feature, hence it makes sense to try to trace how it would have appeared smoothly rather than abruptly. Broadly, we can think of the evolution of consciousness happening in 3 stages: ##### Stage 1: Life emerges 3.7 billion years ago, life emerged in the form of a single celled organism. Even at that stage, life was embodied. That is, from organism's point of view, there was a difference between itself and the external world. The organism was whatever was to be kept in homeostasis and the world was everything else out there. See [Markov blanket](https://en.wikipedia.org/wiki/Markov_blanket) for a perspective on this. Feinberg and Mallet suggests that the subjectivity that arose with the first cell itself is the key to understanding the private nature of consciousness. (That is, why the experience seems to be happening for me subjectively). I find this explanation not sufficient. ##### Stage 2: Simple reflexes for whole body co-ordination of multi-cellular organisms Before Cambrian explosion happened in the period of 550 to 520 million years ago, life was limited to oceans and was pretty simple. Multi-cellular life had originated but it was very basic. When multiple single cells came together as a unit, it became important to rapidly communicate information from one part of the body to another (for say moving the entire body of the organism towards source of food or so on). Diffusion or physiological signals aren't rapid enough for such communication, hence some cells differentiated to neurons that communicated via electric signals. Hence, a simple nerve net powering simple motor reflexes was an intermediate step to consciousness. Fossils records from the Pre-Cambrian era show tracks of a worm which suggested simple wiggly locomotor skills like that of today's worm. If the Pre-Cambrian life was like today's worms, then we can deduce that it wasn't conscious because worms lack detailed senses and don't have enough neurons + there's no isomorphic map of sensory data in the brain + it doesn't show operant learning. If a worm loses track of food trail, it reverts to random search pattern (which suggests it has no sense of where it is in the world). "The nematode nervous system just transforms the immediate sensory environment into immediate motor responses." [Insects have the capacity for subjective experience](https://www.researchgate.net/publication/311770445_Insects_have_the_capacity_for_subjective_experience) ##### Stage 3: Consciousness emerges because it's adaptive It is hypothesized that consciousness appeared along with development of precursors of all modern animal types (vertebrates, arthopods, cephalopods). Why did Cambrian explosion happen where more diversity of life forms got created than it has even been done in Earth's history? The most popular theory suggests it coincided with first appearance of predators. Predators set a arms race where it paid to evolve better senses for both: the one who is hunting and the one who is getting hunted. It is hypothesized that the first sense to develop fully was vision as it gives high-fidelity, precisely localizable signals. Other sensory data got integrated into vision data to create a unified mental imagery for the organism. This addition of detailed sensory data co-evolved with larger brains and bodies as larger organisms defend themselves better. ##### Stage 4: specialization of consciousness Higher order consciousness functions such as expanded memory, self-awareness, reflection and so on would have appeared much later in the process of evolution. #### Adaptive benefit of consciousness Consciousness takes up brain resources which require energy. Hence, primary consciousness would have only emerged during evolution if it would have conferred adaptive benefit to the organism. Here is the list of possible adaptive benefits: - **Disambiguation by integrating multiple senses** - Since sensory data gets integrated within the mental imagery, objects can get disambiguated. For example, you can tell what the object is by its weight even if you can only partially see it. - **Singular motor response via unity of mental imagery** - The more motor responses an organism has available, the more likely it is that reflexes can issue contradictory motor responses (e.g. go right _and_ left). A unified mental imagery enables organism to issue singular, non-contradictory motor responses. - **Predictions of events** - The hierarchical nature of brain that got developed to accommodate consciousness seems to also enable prediction of events in time. It is useful to be able to tell which way and how fast the prey will escape or where will the predator will emerge from. - **Enables flexible behaviors (that are never performed before to situations never encountered before)** - Unconscious reflex => a compiled executable to do one specific action. - Consciousness => a compiler that enables on-demand, flexible programming of desired actions - **Ranks decisions and actions by predicted benefit for survival via emotions / affect states** - The sight of sugar makes us approach it which gives us energy while sight of a predator gives us fear which helps us avoid getting eaten. In short, **consciousness is an efficient way of organizing, integrating and summarizing vast amounts of incoming sensory information for action choices**. #### Smallest brain or brain-like structure capable of suffering Probably a fly, a fly or a mosquito as it's an arthopod. Read [Insects have the capacity for subjective experience](https://www.researchgate.net/publication/311770445_Insects_have_the_capacity_for_subjective_experience) #inbox