Fundamental Issues in Biology

Biological systems are often cited as supreme examples of complexity in nature, and it is not uncommon for it to be assumed that their complexity must be somehow of a fundamentally higher order than other systems.

And typically it is thought that this must be a consequence of the rather unique processes of adaptation and natural selection that operate in biological systems. But despite all sorts of discussion over the years, no clear understanding has ever emerged of just why such processes should in the end actually lead to much complexity at all.

And in fact what I have come to believe is that many of the most obvious examples of complexity in biological systems actually have very little to do with adaptation or natural selection. And instead what I suspect is that they are mainly just another consequence of the very basic phenomenon that I have discovered in this book in the context of simple programs: that in almost any kind of system many choices of underlying rules inevitably lead to behavior of great complexity.

The general idea of thinking in terms of programs is, if anything, even more obvious for biological systems than for physical ones. For in a physical system the rules of a program must normally be deduced indirectly from the laws of physics. But in a biological organism there is genetic material which can be thought of quite directly as providing a program for the development of the organism.

Most of the programs that I have discussed in this book, however, have been very simple. Yet the genetic program for every biological organism known today is long and complicated: in humans, for example, it presumably involves millions of separate rules—making it by most measures as complex as large practical software systems like Mathematica.

So from this one might think that the complexity we see in biological organisms must all just be a reflection of complexity in their underlying rules—making discoveries about simple programs not really relevant. And certainly the presence of many different types of organs and other elements in a typical complete organism seems likely to be related to the presence of many separate sets of rules in the underlying