TABLE 2.
Three emergent levels in the evolution of consciousness, and the new features at each level (adapted from Feinberg and Mallatt, 2019).
| Level 1. Life |
| A. Simplest system that has life is the cell, with bacteria and archaea being the simplest cells |
| B. First appearance: ∼3.7 billion years ago |
| C. Emergent structures: macromolecules (proteins, nucleic acids, sugars, lipids), organelles, cells |
| D. Emergent processes: |
| ∙ The strong boundary condition of embodiment: semipermeable membrane encloses cell contents to concentrate the chemical reactions and keep the reaction products from diffusing away (Morowitz, 2002) |
| ∙ Information-based organization, directed by DNA/genes, and coded to specify the chemical reactions; the gene-coded “purpose” of Mayr (2004) |
| ∙ Metabolism, to convert food to energy (ATP) and make new cellular materials; efficient use of energy and of vital molecules slows entropy (energy waste lost as heat) |
| ∙ Self-upkeep and goal-directed properties (Mayr, 2004; Godfrey-Smith, 2019) |
| ∙ Growth and self-replication/reproduction |
| ∙ Sensitivity and movement |
| ∙ Homeostasis: maintaining a constant internal environment in response to changes in the external environment |
| ∙ Adaptation to the environment |
| ∙ Evolution; natural selection becomes the pruning process that limits the possibilites of evolutionary change and of what features emerge in the system from this level onward (Morowitz, 2002) |
| E. Adaptive advantage of this emergence: world’s first self-perpetuation of complex systems over time |
| Level 2. Nervous systems, From Reflexes Through the Level of Simple, Core Brains (Not Conscious) |
| A. Organisms possessing it: most invertebrate animals; for example, most worms |
| B. First appearance: ∼ 580 million years ago |
| C. Emergent structures: multicellular animal body with different cell types including neurons, neural reflex arcs, sensory receptors, motor effectors (muscles, glands); nerve nets, then a consolidation into central and peripheral nervous system; some of the animals have a simple brain with movement-patterning circuits; the sensory receptors are mechano-, chemo- and photoreceptor cells |
| D. Emergent processes: |
| ∙ Speed: neurons transmit signals fast enough to control the actions of a large, multicellular body in response to sensory stimuli |
| ∙ Connectivity: reflex arcs and neuron networks coordinate all the parts of a large body |
| ∙ Core-brain processes: |
| ∘ Control complex reflexes for inner-body homeostasis |
| ∘ Basic motor programs and central pattern generators for rhythmic locomotion, feeding, and other stereotyped movements |
| ∘ Set the level of arousal |
| E. Adaptive advantages of this emergence: Sustains a large body that can move far through the environment, following sensory stimuli to find food, safety, and mates |
| Level 3. Consciousness |
| A. Organisms possessing it: vertebrates, arthropods, cephalopod molluscs |
| B. First appearance: 560–520 million years ago |
| C and D. Emergent structures and processes: the special neurobiological features of consciousness: |
| ∙ Neural complexity (more than exists in a simple, core brain) |
| ∘ Brain with many neurons (>100,000?) |
| ∘ Many subtypes of neurons |
| ∙ Elaborated sensory organs |
| ∘ Image-forming eyes, receptor organs for touch, hearing, smell |
| ∙ Neural hierarchies with neuron-neuron interactions |
| ∘ Extensive reciprocal communication in and between the pathways for the different senses |
| ∘ Brain has many neural computing modules and networks that are distributed but integrated (separate but highly interconnected), leading to local functional specialization plus global coherence (Nunez, 2016; Mogensen and Overgaard, 2017) (see Figure 3) |
| ∘ Synchronized communication by brain-wave oscillations; neural spike trains form representational codes |
| ∘ The higher levels allow the complex processing and unity of consciousness |
| ∘ Higher brain levels exert more influence on the lower levels such as motor neurons, for increased top-down causality |
| ∘ Hierarchies that let consciousness model events a fraction of a second in advance (Clark, 2013; Gershman et al., 2015; Jylkkä and Railo, 2019; Solms, 2019) |
| ∙ Pathways that create mapped mental images or affective states |
| ∘ Neurons are arranged in topographic sensory maps of the outside world and body structures |
| ∘ Valence coding of good and bad, for affective states |
| ∘ Feed into premotor brain regions to motivate, choose, and guide movements in space |
| ∙ Brain mechanisms for selective attention and arousal |
| ∙ Memory, short-term or longer |
| E. Adaptive advantages of this emergence: |
| ∙ Consciousness organizes large amounts of sensory information into a detailed, unified simulation of the world, so the subject can choose the best behavioral responses |
| ∘ This is a large, effective, expansion of the basic life-property of sensing the environment and responding |
| ∙ With mental maps, one can navigate through space even when no sensory stimuli for guidance are present |
| ∙ Consciousness ranks all the sensed stimuli by importance, by assigning affects to them (good, bad), thereby simplifying decisions on how to respond (Cabanac, 1996) |
| ∙ Consciousness provides behavioral flexibility: adjusts fast to new stimuli so it deals well with the changing challenges of new environments |