a bonobo humanity?

you don’t control this variability

So let me try to understand something completely different, to do with genetics, neurology and selection theory. I’m reading a rather complex, demanding and ambitious book, published back in 1992, by Michael Gazzaniga, called Nature’s Mind, and sub-titled ‘The biological roots of thinking, emotions, sexuality, language and intelligence’. Selection theory gets a regular mention, and I’m assuming what is meant is the Darwinian theory of natural selection. That’s to say, the idea or finding that phenotypic traits that enable individuals in a species to more effectively survive, thrive and reproduce in their particular environment will be ‘naturally selected’ as against other less favourable traits. And so the species will ‘evolve’, that’s to say change, because individuals with the better-adapted traits for a particular environment will out-compete those without those traits and, crucially, pass on those traits to their offspring. Darwin, of course, could only speculate about how those traits were passed down to the next generation, as the whole story of genetic inheritance and DNA wasn’t fully established until well into the 20th century.  

Anyway, Gazzaniga seems to be writing about selection theory as some kind of controversial issue, which surprises me and makes me wonder whether I’m reading him right. So let me focus on Chapter 2, ‘The plastic brain and selection theory’, to help my understanding. Here’s the opening sentence:

Although there is little argument that the selection process is at work at both the molecular and the evolutionary levels in whole organisms, there are major questions about whether the brain develops and functions in accordance with the concept of selection. 

I don’t understand what Gazzaniga means by these separate ‘molecular’ and ‘evolutionary’ levels. After all, evolution just means change of a certain type – that’s to say, changes in organisms. And organisms are, of course, made up of molecules, coded for by genes. So the organisational structure of the brain, down to the molecular level (or upwards from the molecular level), has everything to do with our genetic inheritance. So what, then, are these major questions? Gazzaniga puts it this way: 

…if, as I argue… the majority of our psychological capacities are the result of natural selection, the developing and static adult brain, which houses the neural circuits that enable the human’s high-powered psychological mechanisms to exist, must develop in a surefire, genetically determined way. At the level of behaviour, for example, we want to see whether or not a baby learns to identify a face, or whether there exist in the brain specific circuits enabling facial recognition, circuits laid down by prior genetic forces arrived at through selection pressure. 

So, as I conceive it, Gazzaniga is exploring facial recognition (presumably that of other humans, but ‘face’ isn’t of course restricted to humans) in terms of learning and distinguishing, but also in terms of genes and circuitry that have evolved to render such recognition as vitally important. He cites the Nobel Prize-winning immunologist Niels Jerne’s view that selection operates at the cellular level, even though ‘it might look like instruction occurred at a higher level of organisation’. A ‘signal’ of recognition will prompt a response, once described as ‘unconscious’ (but it seems most scientists today dismiss this as a ‘woo’ word), that has been selected for on the most basic, molecular level. 

So this takes us into a bit of immunology. Jerne used three analogies, as described by Gazzaniga: first, ‘the immune system is forever changed by the appearance of each new antigen, just as the brain is somehow changed by each new experience’, second, ‘each system – brain and immune system, appears to have a memory: when the same antigen presents itself a second time to an organism, the latter produces more and better antibodies’, and third ‘the experience one organism has developed for its immune system is not transferable to its progeny, just as my skiing ability is not necessarily transferred to my offspring’. 

So, to antibodies, and the kappa light chain, which is present in the antibodies of humans and other animals. In all creatures who have these molecules, there is a variable and a constant part of the chain. They’re made up of amino acids, and the constant section is constant for all humans (and presumably for other species), while the variable part varies individually, or ontogenetically. 

It seems that Jerne, and Gazzaniga, have taken this as some kind of analogy for the brain, the plasticity of which has both an ontogenetic (individual) and phylogenetic (species-specific) element. That’s to say, there’s a great deal of ontogenetic plasticity within the brain’s overall phylogenetic structure. I’m not sure if I’m getting this right, though. Here’s more from Jerne, comparing the immune system and the central nervous system:

In the immune system, the constant part of the light chain is obviously laid down in the DNA of the zygote, and it is equally clear that there is DNA in the zygote that represents the variable part of the light chain, although, ontogenetically, this DNA may exhibit an immense plasticity.

In the central nervous system, instincts are also obviously encoded in the zygote, most probably in the DNA. But if DNA acts only through transcription into RNA and translation into protein, and if the phenotypic expression of instincts is based on particular arrangements of neuronal synapses, the DNA through RNA and protein must govern the synaptic network in the central nervous system.

Niels Jerne, ‘Antibodies and learning: selection versus instruction’, 1967

So what to make of this ‘magnificent analysis’ (according to Gazzaniga)? You could say that it’s another brick in the deterministic wall, that ontogenetic plasticity, that which makes me different from you, starts with ‘particular arrangement of neuronal synapses’, or the particular sets of proteins that bring about those arrangements, or, before that…

I’m no doubt being influenced right now by some very recent discussions/arguments I’ve had on the subject of determinism, so I’m probably going further than Gazzaniga intended with his thinking. Or not. I shall continue reading the book to see if he comes to any definite determinist conclusions, or if he even touches on such a touchy subject. 

References

M Gazzaniga, Nature’s Mind, 1992