The Science of Discworld Revised Edition

Whatever the reason, Thompson’s hunch that a real silicon circuit would have more tricks up its sleeve than a computer simulation turned out to be absolutely right.
    The technological justification for Thompson’s work is the possibility of evolving highly efficient circuits. But the message for basic evolutionary theory is also important. In effect, it tells us that evolution has no need for narrativium. An evolved solution may ‘work’ without it being at all clear how it does whatever it does. It may not follow any ‘design principle’ that makes sense to human beings. Instead, it can follow the emergent logic of Ant Country, which can’t be captured in a simple story.
    Of course, evolution may sometimes hit on ‘designed’ solutions, as happens for the eye. Sometimes it hits on solutions that do have a narrative, but we fail to appreciate the story. Stick insects look like sticks, and their eggs look like seeds. There is a kind of Discworld logic to this, since seeds are the ‘eggs’ of sticks, and prior to the theory of evolution taking hold the Victorians approved of this ‘logic’ because it looked like God being consistent. The early evolutionists didn’t see it that way, and they worried about it; but they worried a lot more when they found that some stick insect eggs looked like little snails. It seemed silly for anything to resemble the favourite food of nearly everything else. In fact, it seemed to be a flat contradiction to the evolutionary story. The puzzle was solved only in 1994, after forest fires in Australia. When new plant shoots came up out of the ashes, they were covered in baby stick insects. Ants had carried the ‘seeds’, and the ‘baby snails’, down into their subterranean nests, thinking they were the real thing. Being safely underground, the stick insect eggs escaped the fires. In fact, baby stick insects look, and run, just like ants: this should have been a clue, but nobody made the connection.
    And sometimes evolution’s solution
has
no narrative structure. To test Darwin’s theories thoroughly, we should be looking for evolved systems that
don’t
conform to a simple narrative description, as well as for ones that do. Many of the brain’s sensory systems may well be like this. The first few layers of the visual cortex, for example, perform generalized functions like detecting edges, but we have no idea how lower layers work, and that may well be because they don’t conform to any design principles that we currently can recognize. Our sense of smell seems to be ‘organized’ along very strange lines, not at all as clearly structured as the visual cortex, and it too may be lacking any element of design.
    More importantly, genes may well be like this. Biologists habitually talk of ‘the function of a gene’ – what it does. The unspoken assumption is that it does only one thing, or a small list of things. This is pure magic: the gene as a spell. It is conceived as being a spell in the same sense that ‘Cold Start’ in a car is. But a lot of genes may not do
anything
that can be summed up in a simple story. The job they evolved to do is ‘build an organism’, and they evolved as a team, like Thompson’s circuits. When evolution turns up solutions of this kind, conventional reductionism is not much help in understanding those solutions. You can list neural connections till the cows come home, but you won’t understand how the cows’ visual systems distinguish a cowshed from a bull.
    1 The quantity of bacon per trotter is on average slightly more than quarter of the amount per head.

TWENTY-SEVEN
WE NEED MORE BLOBS

    RINCEWIND WAS FINDING , now that he was back at what appeared to be his real size, that he was coming to enjoy this world after all. It was so marvellously dull.
    Every so often he’d be moved forward a few tens of millions of years. The sea levels would change. There seemed to be more land around, speckled with volcanoes. Sand was turning up on the edge of the sea. Yet the sheer vast ringing silence dominated everything. Oh, there’d be storms, and at night there were brilliant meteor showers that practically hissed across the sky, but these only underlined the absent symphony of life.
    He was rather pleased with ‘symphony of life’.
    ‘Mr Stibbons?’ he said.
    ‘Yes?’ said Ponder’s voice in his helmet.
    ‘There seem to be a lot of comets about.’
    ‘Yes, they seem to go with roundworld systems. Is this a