Edelman (1992: 148-9):
But the brain is subjected to two processes of selection, natural selection and somatic selection. The result is a subtle and multilayered affair, full of loops and layers. From genes to proteins, from cells to orderly development, from electrical activity to neurotransmitter release, from sensory sheets to maps, from shape to function and behaviour, from social communication back to any and all of these levels, we are confronted with a system of somatic selection that is continually subjected to natural selection.
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To be clear, somatic selection in the brain — neuronal group selection — refers to the fact that the firing of a group of neurones increases the probability that the same group — rather than others — will fire again in the future under similar circumstances. It is somatic selection that provides the material basis for semogenesis: the logogenesis of texts, the ontogenesis of meaning potential in (the lifetime of) the individual, and the phylogenesis of language in the species. This can be explained as follows.
From the perspective of Systemic Functional Linguistic Theory, logogenesis provides the 'material' for ontogenesis which provides the 'material' for phylogenesis. The logogenesis of a text involves the instantiation of options in systems of meaning potential. The instantiation of such options increases the probability that these options — rather than others — will be instantiated in the future under similar circumstances. The ontogenesis of meaning potential in the lifetime of the individual thus includes the continual alteration of instantiation probabilities. The phylogenesis of meaning potential in the species thus includes the continual alteration of instantiation probabilities beyond the lifetime of individuals in language communities.
From the perspective of Systemic Functional Linguistic Theory, logogenesis provides the 'material' for ontogenesis which provides the 'material' for phylogenesis. The logogenesis of a text involves the instantiation of options in systems of meaning potential. The instantiation of such options increases the probability that these options — rather than others — will be instantiated in the future under similar circumstances. The ontogenesis of meaning potential in the lifetime of the individual thus includes the continual alteration of instantiation probabilities. The phylogenesis of meaning potential in the species thus includes the continual alteration of instantiation probabilities beyond the lifetime of individuals in language communities.
Importantly, somatic selection systems evolve through natural selection, but linguistic-cultural evolution occurs through somatic selection, not natural selection. Natural selection merely provides the material basis that affords linguistic-cultural evolution.
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