Neural Darwinism
Explanation
Gerald Edelman, Nobel laureate in Medicine (1972) for his work in immunology, devoted the second half of his career to the neurosciences and proposed a revolutionary theory of how the brain is formed and how consciousness emerges: neuronal Darwinism, or the Theory of Neuronal Group Selection (TNGS). The brain is not built according to a preset plan; its circuits are selected by a variant of Darwinian selection.
Three processes are central. First, selection during development: the embryo generates an enormous variability of connections, and those that are used are maintained while those unused are pruned. Second, selection by experience: during life, neuronal groups that mediate successful responses to stimuli are reinforced, and inactive ones weaken. Third, re-entry: neural maps interconnect massively and influence one another reciprocally.
This logic explains why each human brain is unique: there are no two brains with exactly the same circuits, just as there are no two identical immune systems (the immune system also operates by selection of variants). Cerebral individuality is not an accident; it is an inevitable consequence of the construction mechanism.
For consciousness, Edelman distinguished between primary consciousness (the immediate sensation of the here and now, present in mammals and birds) and higher-order consciousness (self-awareness, narrative, linguistic, characteristic of humans). Both depend on massive re-entry between neuronal groups, but higher-order consciousness additionally requires integration with language circuits and semantic memory.
Neuronal Darwinism influenced the dynamic core theory (with Tononi) and, indirectly, IIT. It also connected neuroscience with immunology, evolutionary biology and computational selection models. Edelman tried to build robots (Darwin I, II, III...) implementing his principles, in collaboration with researchers in situated AI.
The theory has critics: some consider the Darwinian metaphor misleading (neural selection is not exactly analogous to genetic selection), others that the notion of neuronal groups is vague, others that the emphasis on re-entry underestimates hierarchical processes. But neuronal Darwinism is one of the most comprehensive theoretical frameworks for how the brain forms and functions, and its intuitions on individuality, plasticity and selection remain valid.
Strengths
- Robust biological framework.
- Explains plasticity and individual variability.
- Precursor of IIT and dynamic core theory.
- Distinguishes primary and higher-order consciousness.
Main critiques
- The selectionist analogy has been challenged as a metaphor.
- Does not directly address qualia.
- Expository complexity hard to operationalise.
- Limited direct empirical reach.