The basic notion that organisms tend to evolve to achieve a maximum fitness has certainly in the past been very useful in providing a general framework for understanding the historical progression of species, and in yielding specific explanations for various fairly simple properties of particular species.
But in present-day thinking about biology the notion has tended to be taken to an extreme, so that especially among those not in daily contact with detailed data on biological systems it has come to be assumed that essentially every feature of every organism can be explained on the basis of it somehow maximizing the fitness of the organism.
It is certainly recognized that some aspects of current organisms are in effect holdovers from earlier stages in biological evolution. And there is also increasing awareness that the actual process of growth and development within an individual organism can make it easier or more difficult for particular kinds of structures to occur.
But beyond this there is a surprisingly universal conviction that any significant property that one sees in any organism must be there because it in essence serves a purpose in maximizing the fitness of the organism.
Often it is at first quite unclear what this purpose might be, but at least in fairly simple cases, some kind of hypothesis can usually be constructed. And having settled on a supposed purpose it often seems quite marvellous how ingenious biology has been in finding a solution that achieves that purpose.
Thus, for example, the golden ratio spiral of branches on a plant stem can be viewed as a marvellous way to minimize the shading of leaves, while the elaborate patterns on certain mollusc shells can be viewed as marvellous ways to confuse the visual systems of supposed predators.
But it is my strong suspicion that such purposes in fact have very little to do with the real reasons that these particular features exist. For instead, as I will discuss in the next couple of sections [6, 7], what I believe is that these features actually arise in essence just because they are easy to produce with fairly simple programs. And indeed as one looks at more and more complex features of biological organisms—notably texture and pigmentation patterns—it becomes increasingly difficult to find any credible purpose at all that would be served by the details of what one sees.