One circumstantial piece of evidence is that one already sees considerable complexity even in very early fossil organisms. Over the course of the past billion or so years, more and more organs and other devices have appeared. But the most obvious outward signs of complexity, manifest for example in textures and other morphological features, seem to have already been present even from very early times.

And indeed there is every indication that the level of complexity of individual parts of organisms has not changed much in at least several hundred million years. So this suggests that somehow the complexity we see must arise from some straightforward and general mechanism—and not, for example, from a mechanism that relies on elaborate refinement through a long process of biological evolution.

Another circumstantial piece of evidence that complexity is in a sense easy to get in biological systems comes from the observation that among otherwise very similar present-day organisms features such as pigmentation patterns often vary from quite simple to highly complex.

Whether one looks at fishes, butterflies, molluscs or practically any other kind of organism, it is common to find that across species or even within species organisms that live in the same environment and have essentially the same internal structure can nevertheless exhibit radically different pigmentation patterns. In some cases the patterns may be simple, but in other cases they are highly complex.

And the point is that no elaborate structural changes and no sophisticated processes of adaptation seem to be needed in order to get these more complex patterns. And in the end it is, I suspect, just that some of the possible underlying genetic programs happen to produce complex patterns, while others do not.

Two sections from now I will discuss a rather striking potential example of this: if one looks at molluscs of various types, then it turns out that the range of pigmentation patterns on their shells corresponds remarkably closely with the range of patterns that are produced by simple randomly chosen programs based on cellular automata.

And examples like this—together with many others in the next couple of sections [6, 7]—provide evidence that the kind of complexity we see in biological organisms can indeed successfully be reproduced by short