The Science of Discworld IV

dramatically. Some experts think that the increase in power will shortly have to slow down, but others remain convinced that new ideas, often already visible, will keep it going.
    Our culture sometimes seems to follow evolutionary trajectories too. As individuals, we respond to the cultures in which we live, and we are conducted into our technological future as it changes progressively. As far as cultures go, this is an evolutionary process. From a human viewpoint, however, such progressive change looks like the development of a more complex living system, a socio-dynamic. Is technology cancerous, born of mutation as it burst out of its hunter-gatherer background, as it evolves into new forms? Or is it developmental, exploiting new organisations as it invents thembut maintaining an adaptable but stable path, just like a developing embryo? An embryo destroys many organised structures, and kills many of its cells, as it develops. It builds scaffolding and throws it away when it is no longer needed.
    From the point of view of the individual human, caught up in a technological rat race, this stress is clearly a symptom of social pathology, as Alvin Toffler argued in
Future Shock
. In contrast, looked at culturally, it is natural development. This difference of viewpoint resembles the two ways to describe a thinking mind: nerve cells and consciousness. More generally, not only can every complex system be described in several non-overlapping ways: it can also be described on several levels … as concrete or as a bridge; as an architectural bridge or as a weak point for an enemy invasion.
    Human evolution occurs on two levels: embryological development and cultural development. Neither process is preformational, with all necessary ingredients already present. Neither is a straightforward blueprint: make it like
this
. In both, evolutionary changes occur through complicity between several programmes, each of which affects the future of the others. As time passes, each programme not only affects its own future by its own internal dynamics: it also changes its future by the changes it causes in the other programmes.
    To what extent are those changes predictable or accidental? There is a difference here between two modern viewpoints, one associated with the palaeontologist Simon Conway Morris in
Life’s Solution: Inevitable Humans in a Lonely Universe
, and the other with the late Stephen Jay Gould in
Wonderful Life
. This difference is crucial to the issue of design in evolution.
    Gould made great play of the variety of the animals represented by the fossils in the Burgess Shale, deposited at the start of the Cambrian period about 570 million years ago. These fossils had been described by previous biologists, but Morris reworked and reconstructed them. He classified these fossils into a wide range of morphological types; infact, many more basic kinds of animal design (‘phyla’) than had been assigned previously. Gould used this wide range of body designs, only a few of which have descendants among present-day creatures, to argue that life can do almost anything by way of morphology, even in its fundamental or basic structure, and that the organisms that now exist are accidental survivals from the much vaster range that existed at the start of the Cambrian.
    Morris, however, has come to believe the opposite, namely: because some of the many themes have converged to produce similar beasts, some specific designs must be winners, no matter how they are realised. Therefore any wide array of different body structures will necessarily evolve to generate much the same spectrum that we observe today, automatically selected because those are the body-plans that work best. The fossil record contains many cases of this kind of convergence: fn3 ichthyosaurs and dolphins have evolved to look like sharks and other carnivorous fishes, because that’s the shape that’s most efficient for a fishy predator. In short, Morris believes that if we were to find living creatures on a similar planet to Earth, or if we were to run Earthly evolution again, then much the same range of animal designs would appear. Aliens on a world like ours would be much like us, even if their biochemistry were totally different.
    In contrast, Gould believed, as we do, fn4 that in such a rerun the resulting spectrum of life forms would not resemble the current ones at all. Different designs, fundamentally different body forms, would be just as likely as the ones