The Science of Discworld IV

single innovation that marked biotic from pre-biotic, it would be the ribosome, the translator supreme. Barbieri thinks the ribosome is central to life, and so do we. DNA is simply the rather prosaic, boring text. The ribosome is the orator; the other RNAs are the poetry. Once the ribosome emerged, the future became a living future, and in many ways this step marks the true origin of life.
    Most origins also involve more subtle forms of emergence: the beginning of a storm, the acorn’s origin as a bud on the oak, the origin of the Earth. Each of these origins is a quantitative-to-qualitative transformation, an emergent event that localises a real beginning. The first stroke of lightning, the first pair of leaves, the generation of heat that melts the core inside the Earth’s mantle: these are emergent events that can label beginnings of new structures. The ‘becoming’ has divided into two issues, before and after the emergence.
    If a phenomenon is emergent, it transcends all that has gone before. It does something that its bits and pieces could not have done on their own, or partially assembled, or assembled with some extra scaffolding that gets in the way. This transition is often the best stab we can make at assigning an origin. An emergent phenomenon does not originate in the bits and pieces that led to it: it originates when it emerges.
    The emergence of the first lightning strike marks the beginning of the storm. The cell divisions that mark the acorn’s difference from the other buds around it are the emergent oak. The cell divisions and relationships that promoted the egg that later became you orchestrated the emergent event that began you. The universe is complicated because emergent events – quantitative differences becoming qualitative differences – have occurred so many times.Bridges like ribosomes have been built, and the Moon now circles the Earth.
    These links have joined separate events into a web of causality that is the most notable property of the world around us. A story, however, is not a web. It has a linear structure, because both speech and writing proceed one word at a time. Even hypertext, used on the internet, is determined by a linear programme written in hypertext mark-up language (html). And that is why storytelling – human narrativium – finds origins to be so difficult and puzzling, and sometimes looks for simplicities where none exist.
    fn1 Junjun Zhang, Nicolas Dauphas, Andrew M. Davis, Inigo Leya and Alexei Fedkin, The proto-Earth as a significant source of lunar material,
Nature Geoscience
5 (2012) 251-255.
    fn2 Harald Brüssow, The not so universal tree of life
or
the place of viruses in the living world,
Philosophical Transactions of the Royal Society of London
B 364 (2009) 2263-2274.

ELEVEN
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A VERY INTERESTING CASE

    Mustrum looked at Miss Daw with a slightly sorry expression, which burst into a smile. ‘Going home, then? Well now, isn’t that good news? I’m sure your people there will be wondering what has happened to you, though of course you needn’t worry – we can put you back right at the point where and when you left. Such a pity you couldn’t stay longer; it is always useful to talk to somebody who knows how to talk.’ Ridcully sighed. ‘It isn’t easy being Archchancellor. Very few people will talk to you as if you are a human as opposed to a very large hat; you just have to hope that there is somebody ready and willing to tell you when you are making a bloody fool of yourself.’
    He sighed again, and Marjorie said, ‘Would you mind if I stayed a little longer, then? I mean, if you can send me back home as if this never happened, well, it’s a long time since I’ve had a holiday, and I’m fascinated by what is happening here. After all, it appears that there is going to be a major court case to see who owns my planet. So excuse me if I demand a ringside seat, since I am a sitting tenant, as it were. I could earn my keep too; although I say it myself, I am well versed in all aspects of library practice. But
really
, surely some representative of the population of the world in question should in all fairness be allowed to at least follow the proceedings.’
    Ponder Stibbons glanced at the Archchancellor and said, ‘She might have to wear a beard, Archchancellor; it
is
laid down bystatute.’ The air thickened a little, and he kept a weather eye on Ridcully’s face.
    Slowly the Archchancellor said, turning over every letter like some