The science of discworld.., p.21
The Science of Discworld IV, page 21
So let’s conceive.
A number of biologists have attempted to deduce a plausible or likely evolutionary route to a bacterial motor, from DNA and other biochemical evidence. This turns out not to be especially difficult. Many details are still provisional, as is all science, but the story is now sufficiently complete to disprove the contention that the motor exhibits a type of complexity that rules out all evolutionary explanations. Agreed, that doesn’t prove that the current evolutionary explanation is correct. That must be confirmed, or denied, by further scientific investigations. But it’s quite different from asking whether, in principle, any such explanation can exist.
The most fully developed synthesis of these proposals, put together by Nicholas Matzke, starts with a general-purpose pore. This evolves into a pore with more specific functions. At this early stage, the structure is not a motor, but it already has a very useful, entirely different, function: it can transport molecules out of the cell. In fact, it is recognisable as a primitive version of so-called Type III Export Apparatus, which exists in modern bacteria, and DNA sequences support this. Further changes, in which the pore’s function is successively improved, or changed by exaptation, provide an entirely plausible evolutionary route to the bacterial motor, increasingly supported by DNA evidence.fn6
Yes, if you take away enough parts of the bacterial motor, then it might not be a very good motor any more. But evolution didn’t know it was supposed to be making a motor.
So ‘design’ isn’t what it is often thought to be, even for human technology, let alone biology. Each innovative step may be driven by human intentions, but what works, and what passes on to later technology, evolves. To some extent, cars evolved from horse-drawn carriages, and a ballpoint pen is the lineal descendant of a quill made from a feather. We can legitimately compare these developments to mammals evolving from a Devonian fish that came out of the water onto land, or to our little middle-ear bones being the lineal descendants of bony gill structures in that fish.
Evolution is not efficient. It throws an awful lot of things away. Innumerable land vertebrate species have gone extinct. Similarly, most human designs don’t work. From the enormous number on offer, only a few develop into sophisticated structure/function niches. We are all bound by tradition, as well as by functional constraints that require any new development to fulfil the same functions as its ancestor. There’s a classic example: Apollo rockets were moved to their launching-pads on rails that were much too close together for stability, because the gauge of America’s railways came from mine railways that were two horses wide. So the Moon project was jeopardised by horse’s asses.
To be specific, let’s think about better mousetraps. Mousetrap evolution is a process, not just a succession of models; it branches into the future. The pattern that has a metal bar coming down and (one hopes) breaking the mouse’s neck, has expanded into dozens of different models, some computer-controlled. Those that trap the mouse in a metal tube, or a cage, are more like descendants of lobster-pots, but these too have performed what biologists would call an adaptive radiation: we found seven different kinds, with sprung doors or elastic apertures for entry.
The same goes for bicycles, cars or computers: they all adaptively radiate into the future. Each new ability, such as computer control – a logic chip – on a particular technical road branches into new roads. Think of the familiar cat flap, now available in versions that allow your own cat, wearing its magnetic collar, in or out, but exclude foreign cats. Or fancy electronic ones that verify your cat’s ID. Full-body scanners to detect terrorist cats carrying exploding mice cannot be far away. Just as in organic evolution, the adjacent possible is continually being invaded: possibilities just one step away from current practice are tried, rather unoriginally.
We usually think of this as technical development, not innovation, unless it is in an unexpected direction: Teflon used for non-stick frying-pans, or penguins’ wings used for swimming. Most aquatic vertebrates, unlike these birds that have become secondarily aquatic, use their tails, not their fins, for propulsion. Such more original changes of direction are best thought of as exaptations rather than adaptations. Or, to use a less biological term, genuine innovations.
Among those who accept evolution as a reasonable metaphor for many examples of progress in technology, it used to be thought that the major difference between technical and organic evolution is that technological evolution is Lamarckian – named after the French naturalist Jean-Baptiste Lamarck, a contemporary of Darwin – whereas organic evolution is Darwinian. In Lamarckian evolution, acquired characteristics can be inherited – if a blacksmith acquires strong arms because of his work, his sons should also have strong arms. In Darwinian evolution, that’s not possible. Neo-Darwinism illuminates the difference: heritable characteristics are those that are determined by genes.
Lately, this distinction has become a bit blurred, and each mechanism has acquired features that were thought to be characteristic of the other. Technical development has borrowed a trick from evolution to construct so-called genetic algorithms for the development of new products. Digitised designs are shuffled, by analogy with recombination, the way biological reproduction shuffles gene variants from both parents. The next technological generation to survive this process combines the more useful features of previous generations. Sometimes it has new emergent properties, which are selected if they prove useful, and are retained. Often the final design is incomprehensible to a human engineer. Evolution need not obey human narrativium.
The phenomenon of genetic assimilation, which is entirely Darwinian, can look very Lamarckian. Changing a population progressively by selecting genetic combinations that work can change the thresholds at which particular capabilities come into play. As a result, effects that originally depended on some environmental stimulus can happen without that stimulus in later generations. For example, the skin on the soles of our feet gets thicker when we walk regularly, an acquired characteristic; however, genetic recombinations that provide babies with thicker skin on their feet from the start make this process more effective, and so are selected for. Any new feature, acquired or not, that works – that improves the chances of surviving to reproduce – reveals a feature that Darwinian evolution could blunder into and exploit. Genetic assimilation may indeed be the usual way that originally responsive adaptations get built in to the developmental schedule.
In particular, the old distinction between Lamarck and Darwin has lost its power to distinguish technical from organic evolution. But that doesn’t imply that there are no significant differences. It’s tempting to think that one obvious aspect of technological evolution surely can’t apply to Darwinian evolution: imagining a possibility before designing a technique or gadget to implement it. Human technology is born in the imagination of a series of inventors or discoverers: ‘What would happen if …?’ is a theoretical exploration of Kauffman’s adjacent possible. Much of the time, imagining possibilities leads to hypothetical new inventions being rejected without bothering to make them or test them: they wouldn’t work because … or no one could use them because … or they would be too expensive … or they wouldn’t perform well enough to displace the widget that already does the job very well.
It doesn’t seem possible that this imaginative process could have an organic analogue – but it does. In 1896 the psychologist James Mark Baldwin wondered whether animals carrying out behavioural experiments might be drawn into the evolutionary process, in effect by imagining what would happen if they could perform some new task that was actually beyond them. For instance, an okapi is like a giraffe, but its neck and legs are of normal length. Suppose that an adventurous okapi, for example, kept reaching up in an attempt to browse on the lowest branches of trees, despite repeated failure. Because it failed, this would be analogous to imagination. But occasional success could favour okapi with slightly longer necks and legs, leading to a giraffe. This process is often called the Baldwin effect.
A few years ago, we observed some animal behaviour that could well become the root of such an evolutionary trajectory – an exaptation in the making. Plecostomid catfish (‘plecs’) are common scavengers in larger aquariums, cleaning algae off the glass with their sucker-like mouths. In the wild, they can hold tight to smooth rocks as they glean the algal film; they also have effective armour with barbed bony supports in their dorsal and pectoral fins. In aquaria, these characteristics give them an entirely different ability, which we saw a plec exploiting in the Mathematics Institute common room at the University of Warwick. This plec’s natural abilities made it much better than other fish at garnering floating pellets of food. It did this using a method quite alien to wild plecs: it turned on its back and used its sucker-mouth to take in soggy pellets, while its spiky fins kept off the competition. So a catfish mouth, adapted for taking food from rocks, can be exapted to take food pellets from the water surface, especially if the fish concerned has effective defences, and the food is soft.
Future genetic assimilation could easily build this kind of exapted behaviour into the genes of the plec population. It could be selected for, and then adapted along an evolutionary trajectory, so that a plec would take food from the surface normally in just this way.
In fact, something of the kind has probably happened already – though not in descendants of the Mathematics Institute plec, which had none. The fish in question is the upside-down catfish Synodontis nigriventris,fn7 which takes insects from the surface of the water in the wild using a similar technique. We have, then, both ends of a plausible evolutionary trajectory. It starts, perhaps, with a hungry catfish alerted to a food mass on the surface, near it in shallow water; perhaps a rotting, floating insect carcass. The catfish turns over in its attempts to get its mouth near to the tempting morsel, and even if it mostly makes a hash of this, any occasional success is rewarded. It will now be sensitised to this source of food, and might haunt the shallows for more of them. Its offspring, growing up in the same environment, are then more likely to be selected for similar behaviour if genetic changes can make it more effective.
This scenario contradicts Stephen Jay Gould’s assertion in The Flamingo’s Smile that adaptations like the upside-down feeding of the flamingo, scooping up crustaceans from saline lakes, must involve a single radical departure from the normal use of the beak. Animals can try out little behavioural experiments, and if they are rewarded, these can become built into their subsequent behaviour. Then, if the reward is as important as a new source of food or novel access to mates, natural selection can improve it.
Technical evolution can avoid such time-wasting, progeny-wasting, and new-function-wasting aspects of organic evolution in two ways. The first, we have discussed already: human minds can attempt to jump into the adjacent possible and see if it works ‘in the imagination’. Can we imagine an aeroplane ten times the size, and what would need to be changed for it to work? If we exaggerated the length of a bicycle frame and had the cyclist lean back, how could he see the road? Do we then want him on his front? Both have been tried, and are excellent examples: technical results of our imagination playing in the adjacent possible.
The other trick that minds can do to improve technology is to copy: to take a technical trick used in one invention and to spread its use to others. That trick, except for a few cases where genes have achieved horizontal transfer between species, is impossible for organic evolution: each lineage must invent for itself. A recent spread of this kind has been the use of digital switches in a variety of machines from toasters and children’s toys to automobiles. The big one before that was the use of plastics to replace metals in the nursery, kitchen and laboratory. Before that, transparent plastics, mostly acrylics, had been used to replace glass in many applications. The progressive use of semiconductor technology is giving us solar panels, tiny refrigerating or heating elements, and a new family of very efficient light bulbs: white-light LEDs. Banks of coloured LEDs can now be tuned to give different lighting conditions; bright white light is not conducive to sleep and can be replaced with softer tones. Flexible television/computer screens, which can be rolled up like paper, already exist in the laboratory, and are not far from commercial production. An entire book has just been encoded in DNA, and a human face has been printed on a human hair.
In biological evolution, it used to be thought that environmental ‘niches’, such as predatory behaviour, were already available and waiting to be occupied, rather as though some cosmic script had already written down all the possible things that an organism might do. Now it is thought that organisms construct niches as they evolve; for instance, you can’t occupy the dog-flea niche until there are dogs.
Even taking copying into account, the analogous questions of competition and niche-construction in technology are as important as they are in the natural world, and they too force the evolution of new products. A good example was the colonisation of the marketplace in the 1970s by VHS videotapes, even though its rival Betamax was much better in several respects. As in natural ecologies, it often happens that a less-adapted, often foreign, invader exploits the ecosystem more effectively, forcing the demise of well-established local species. The grey squirrel, for example, carries a disease that decimates indigenous red squirrels, much as the Spanish invaded South America and destroyed Inca and Maya empires. The red squirrel was better-adapted to its original environment, but the arrival of the invading grey squirrel changed that environment; in particular, it now included grey squirrels and their disease organisms. The change was sudden, biological warfare rather than the usual sedate pace of natural selection in a slowly changing environment.
In the technical world, then, there do exist processes resembling those of organic ecosystems. Many of them are recursive, affecting their own development: supermarkets make their own ecosystem of consumers, just as dogs create a new niche for dog-fleas. This makes questions about the design of technology much more difficult, because there are few real innovations, but many exaptations, copyings and adaptational trajectories. Only a few really novel tricks can be claimed to have a human designer in a non-evolutionary sense.
There is a trajectory of development for a technological product: a car starting from carriages and an engine, steam or internal-combustion; a radio starting from a crystal set and headphones; a bicycle starting as a penny-farthing and evolving through the sit-up-and-beg still seen all over China and India to the mountain bikes and lie-down versions of the latest adaptive radiation.
These are paths through our cultural history, and they make their own contexts as they evolve. The car creates vast and important areas of our cities where cars are built, where auto workers live, where the suppliers of parts have some of their factories and warehouses. When we give little Johnnie a bicycle on his seventh birthday, we introduce him to a new world that has grazed knees, gears, punctures, comparison with Fred’s bike … When the transistor radio erupted into Western culture in the 1960s, it changed the relationships of teenagers to each other and to pop stars, though nothing like as much as the mobile phone has changed all of our lives in the last few years. Alexander Graham Bell, on a promotional tour of his invention the telephone, so impressed one city’s mayor that he is said to have declared: ‘What a wonderful invention; every town should have one.’
Artefacts evolve, and the functions they perform get better, wider, cheaper. But they also change the society around them, so that their ‘improved’ next generation already has the ground prepared for it. The Ford Model T would not have been viable without gas stations, which had appeared to service the much more expensive previous generation of automobiles. In turn, the Model T and other similar affordable automobiles with privacy in the back seat changed much of the sex life of the young men and women who had access to them. Society’s rules change as the Ford Model T, the transistor radio, central heating, subway travel and mobile phones affect their context, and the context in turn constrains or directs the further evolution of the product.
Nearly all inventions don’t follow that kind of successful path; like nearly all species of organisms, they prosper for a little while but then die out. The few that do survive find a trajectory that takes them into the future. Frequently they move into a whole new phase space of possibilities, where their original design is effectively useless, but the new world now has an improved design. Like a genuine Stone-Age axe that’s had its handle and blade changed several times, we find a new world with a new artefact and a new function.
In The Science of Discworld III we described how apparently rigid limitations on the energy needed to put a person or cargo in orbit around the Earth could, in principle, be overcome by changing the context. If you use a rocket, the amount of energy needed to get a 100-kilogramme man up to synchronous orbit can be calculated using Newton’s laws of motion. It is the difference in potential energy caused by the planet’s gravity well. You can’t change that, so at first the limitation seems foolproof.
In the mid-1970s, however, a wholly new suggestion was made: the space bolas. Essentially this is a giant Ferris wheel in orbit. The traveller gets into the cabin as it swings past the upper atmosphere, and gets out again when it approaches the furthest point from Earth. A succession of such gadgets can deposit him in synchronous orbit a few weeks later.
A third step in the ladder of technology, not practical yet but already being discussed by engineers, is the space elevator. The science fiction writer and futurologist Arthur C. Clarke was one of several people who had this idea: take a ‘rope’ up to synchronous orbit and let it down to an equatorial landing-strip. The result would be a material link from a point in synchronous orbit to the ground. Once this is set up, a system of cabins and pulleys-and-weights like those used in skyscraper elevators could take a person up to orbit very efficiently. Counterweights, or another man coming down, would reduce the cost to that of the energy required to override friction.
