The Bootstrapped Brain: Evolutionary Change Through Socialisation and Brain Plasticity
2024/10/27
This is a hypothesis that I wrote up ±15 years ago, that I did not publish as there is no appropriate venue (journal) for hypothetical ideas like this. I find that to be a pity, and there's a gap. I hope that you enjoy this idea.
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It has been proposed by Stedman et al that the loss of jaw muscle mass might have allowed for an increase in the cranial capacity of early humans.
How could this change have given this mutant group any sort of advantage? The weaker jaw muscles would no doubt lead to weaker, inefficient hunters. We argue that this increase in capacity might have allowed for some swift change in the cranial capacity of early humans, and, as such, a small cognitive advantage to these otherwise seemingly weaker apes. Therefore, a genetic change in brain size was not necessarily immediately required for the advantage of these early humans. In broader terms, we argue that socialisation coupled with the plasticity of the brain does away with the absolute requirement of a 'step' change in the evolutionary sense.
A number of people who dispute evolution argue that the step changes of the magnitude required to differentiate a modern human from an ape do not occur in nature. It is, of course, absurd to think that a step change occurred and that in one generation a line of apes became human. The genetic changes required to necessitate the modern thinking and communicating human are numerous and have been quantified, and the statistical probability of this occurring simultaneously in order to allow an advantage to the human seem fairly proposterous. However, a single change as proposed by Stedman et al could reveal the answer - and this is not only a bigger eventual brain in the physical sense. The answer lies in the idea that the brain can boostrap.
It is well known that the brain has high plasticity - it conforms and changes according to environmental stimuli. Free neurones independently begin to form independent functional networks based on the environment in which they are placed. Research into rat neurones in a petri dish interfaced with a flight simulator have shown that the neurones are capable of forming and learning based on these changes.
The very fact that individuals could create a wider range of sounds using their mouths may have lead to their own cognitive development. There may be positive feedback in the sense that making more complex sounds lead to stimulation of the brain's communication centres, and in turn stimulation of the brain lead to the ability to make more complex sounds.
Then, there is socialisation. The knowledge of the previous generation could be passed on, in more complex ways, via more complex communication. This does not require a genetic change, it relies entirely on the plasticity of the brain. The physical brain growth may have come later, and this may have been naturally selected for humans based on their increased problem solving capacity. The ability of individuals to communicate better, and the very fact that a wider variety of sounds through freedom in articulation may have shaped the young mind of the next generation. Immediately, this training through socialisation from a young age when the brain's plasticity is high would have lead to an increased sharing of thoughts and ideas. It is not just this sharing of thoughts and ideas that may have lead to increases in early humans' capacity, but the very process of training and speaking that caused through stimulation conformational changes in early human minds.
This theory is not easily testable. It might help, but is not necessarily sufficient, to splice the gene for weaker jaw muscles into a pygmy chimp and observe the changes. This, however, has to be coupled with the socialisation aspect of the development of the chimp.
It is not clear to what extent epigenetics may have impacted here - the rapid change induced by the cognitive change through socialisation and brain plasticity in early humans may have translated to a rapid depositing of epigentic factors. This might mean that the changes experienced did translate to rapid genetic change - thus speeding up the evolutionary process down the progeny line. As argued here, however, the rapid change in genetics is not required once more freedom in communication ripens. It is the plasticity of the brain, propagated through self-stimulation, socialisation and mutual group stimulation, that may have lead to early humans relative advantage in a climate in which fitness was essential.