Noises from the Darkroom: The Science and Mystery of the Mind. Guy Claxton

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      Walkie-Talkie

      In simple multicellular creatures, a nervous system that keeps the different subsystems directly in touch with one another will do well enough. They can talk to each other by CB radio, without having to invest in any central administration. The Portuguese man-of-war, for example, is technically speaking not a single creature but a large sticky conglomerate of interdependent organisms who have decided to throw in their evolutionary lot with each other. Some of these are specialized for floating and providing buoyancy. Others engage in collecting and digesting of food, or in sensing different forms of incoming energy (who can tell by the stimulation of the water whether there is anything interesting in the vicinity, and if so whether it is likely to be a meal or an enemy). Others specialize in mounting guard and manufacturing ammunition for the poisonous tentacles. And others in planning and preparing for reproduction. This colony manages to co-ordinate its complicated set of senses, activities and needs without any central information point, or sophisticated nervous system, simply by enabling various sensory and response subsystems to talk directly to each other.¹⁷

      Beyond a certain degree of complexity, however, this point-to-point form of communication begins to become cumbersome and inadequate. The system as a whole needs to be able to hold ‘conference calls’, as well as allowing each department to talk directly with one another. So evolutionarily there is a move towards greater ‘networking’ between the different systems, and eventually towards some kind of centralization – an office, like that which controls a fleet of taxicabs, which can keep an overview of what is going on, and co-ordinate the different activities. And at this point the distributed nervous system begins to develop into a ‘central nervous system’, the CNS. Not that there has to be any controller who sits in the ‘head office’, deciding what is best. The design of the animal CNS, and ultimately of its brain, as we shall see, is such that this kind of centralized decision-making about what is best for ‘all-of-me’, can be conducted very well by a communication system that is wired up in clever ways, so that the wiring itself determines how choices are made. No ghost in the machine is required.

      Getting Around

      One of the evolutionary moves that must have stimulated the development of the first brains was mobility: the discovery of the advantages of being able to get about. Couple mobility with a sensory system, and you are able not just to close your mouth and hold your breath when something nasty comes along, but to get out of the way. You are not dependent on what the stream happens to be serving that day; if you don’t like it you can go and see what is available at the restaurant across the road. But there are also inherent questions and problems associated with being mobile. Do you become nomadic, of no fixed abode, or do you have a home that you return to each evening after a hard day running about chasing things? Either way there are pros and cons.

      If you were a tunicate – a sea squirt – for example, you would have opted for an interim solution. The young sea squirt is a tadpole-like larva that possesses a primitive brain, which can be informed about what is going on by an organ of balance (such as we humans have in the middle ear), and a simple eye. It is equipped to navigate its way through changing aquatic conditions whilst engaged in a process of once-and-for-all house-hunting. When it finds its ideal home, the sea squirt gratefully settles down for life, and turns itself back into a plant by the simple expedient of eating its now redundant brain. (It has been suggested that this behaviour parallels that of university academics on finally obtaining a tenured appointment.)¹⁸ We might also note, to anticipate later discussions, that the issue of what to do with a brain that has evolved to a level of power that is out of all proportion to the current survival demands – when a species finds that, for a while, it has ‘got it made’ – is one that bears on the contemporary situation of homo sapiens. Eating a good chunk of the brain seems a solution to the problem that it might pay us to consider.

      Sophistication and The

       Proliferation of Needs, Part 1

      The major components of the mammalian survival kit are sometimes (rather coarsely) referred to as the Four F’s – flight, fight, feed and mate – in approximately that order of urgency.¹⁹ If a predator appears, make yourself scarce. If you are cornered, or are trapped by the over-riding need to defend territory or young, stand your ground and see them off. When it is safe enough to do so, turn your energies back to the perennial search for sustenance. And if these other claims are assuaged for the moment, and the time is ripe, let your fancy lightly turn to thoughts of procreation. Each of these general departments ramified into elaborate rituals, and intricate signalling systems evolved to get these survival jobs done with the minimum of risk and inconvenience.

      As the nervous system, and the body that it serves, grows in complexity, so the behavioural repertoire gets broader and subtler, and the sophistication with which different actions can be selected for different contingencies gets higher and higher. But at the same time, the vulnerability of the creature also increases. Sophistication aids survival, but it also calls into being new threats to survival. The more intricate a machine, the more ways there are in which it can break down. Choosing the evolutionary path of becoming high-tech means that the basic drive to survive and reproduce fragments into dozens of secondary and tertiary priorities.

      For example, the more delicate your constitution, the more things there are that might upset you, or even kill you, if you ingest them by mistake. So your appetites, and sense of taste and smell, need to develop to provide an adequate level of protection. (And if you live in an environment that teems with chemicals that have not coevolved with you, and so there has not been the evolutionary time for knowledge of their risks and benefits to be incorporated into your preferences and aversions, you will be at risk, especially from those chemicals that are harmful in the long term – which decrease your fertility, for example – but which produce no short-term effect for you to learn from.)

      If you have evolved a skeleton to support a big body, you are at risk from breaking bones. The more delicate your bits, the more carefully wrapped they have to be. If you developed a circulation system to carry oxygen to all those cells who work deep in the livermines, then they, and all the other underground workers, are at risk from any passing cloud of molecules that happen to bond more strongly to haemoglobin than oxygen does. If you grew lungs to get the oxygen into the right sort of contact with the blood, you can be beaten at your own game by a virus that makes the lung surface weep thick mucus, so that, like fish who drown when oil is spilt on the surface of their pond, you are disconnected from your vital power source.

      If you have developed fast legs that enable you to outrun predators (rather than sharp teeth to see them off, and thick skin to minimize the danger of being punctured in a fight), you have to be able to see them coming, and are therefore vulnerable to twilight and cataracts. And if you have evolved an immunological secret police, who recognize and execute any enemies who have infiltrated the palace, you become all the more vulnerable when they go on strike, or worse, when they run amok and start attacking honest citizens (or each other).

      Each new threat constitutes another priority that the system as a whole has to take into account in planning its next move. Any course of action is liable to disruption before it is complete. A snake may suddenly appear, or the urge to defecate slowly grow, and the response to each has to take into account the other priorities, the opportunities currently afforded by the world, and the range of available options for action. Should I stop chasing that gazelle and pay attention to the pain in my foot? Can I safely take a nap here, or should I wait till I get home? Am I likely to find a familiar snack on the way, or should I eat these berries now, even though they taste a bit funny? The more diverse your portfolio of requirements, the more you need a brain to keep track СКАЧАТЬ