Life as Supple Adaptation

Mark Bedau has recently proposed an extreme evolutionary definition of life (e.g. [Bedau 96], [Bedau 98b]). Nearly all other definitions, whether evolutionary or ecological, see life primarily as a property of individuals (be they organisms, cells, or genes). In contrast, Bedau claims that a system capable of open-ended evolution (or `supple adaptation' to use his phrase), in its entirety, should be considered as the primary form of life. A system exhibits supple adaptation by the ``ongoing and indefinitely creative production of significantly new kinds of adaptive responses to significantly new kinds of adaptive challenges and opportunities'' [Bedau 98b] (p.127). Bedau continues: ``a supplely adapting system is an evolving population of organisms, or a whole evolving ecosystem of many populations, or, in the final analysis, a whole evolving biosphere with many interacting ecosystems'' (ibid. p.131). In this view, particular components within the supplely adapting system, such as individual organisms, qualify as (secondary forms of) life by virtue of their specific relationship with the system. Exactly what relationships are required between a component and the system for the component to qualify as being alive is an open question. In suggesting this definition, Bedau emphasises that ``natural selection is not sufficient for supple adaptation ... natural selection produces supple adaptation only when it is continually creative'' (ibid. p.127).

At first glance, Bedau's suggestion might appear similar to James Lovelock's `Gaia' hypothesis, that the whole Earth is equivalent to a single living organism [Lovelock 79]. However, the similarity is only superficial. Lovelock sees the Earth as a homeostatic, self-regulating entity; in other words, something which has the properties that we commonly associate with more standard biological organisms. Bedau, on the other hand, is certainly not claiming that the biosphere has these properties; what he is claiming is that the world must have a certain set of properties which enable it to act as a supplely adapting system if it is to be able to support the evolution of living (in the common sense of the word) organisms.

Bedau himself acknowledges that many obstacles must be overcome before a satisfactory definition can be produced in these terms, but claims that the approach has promise for providing good explanations for a number of fundamental puzzles about life. The primary interest of his proposal in the present context is that it defines (secondary forms of) life as being the product of the right kind of evolutionary process (i.e. one capable of supple adaptation), rather than of evolutionary processes in general. The precise characterisation of the kind of evolutionary process which might possess this capacity is an endeavour requiring much further work. The intriguing implication is that many of the specific phenomena related to biological life which are not usually associated with purely evolutionary definitions (e.g. self-maintenance, food webs, etc.: see Section 2.1.2) might actually be necessary features of any system capable of supple adaptation. In this way, such features might ultimately be incorporated into an evolutionary framework of the type suggested by Bedau. Of course, this is just a theory, like any other, but it is worth serious consideration. We will return to this topic in Chapter 7. In the following section we return to more traditional individual-based approaches, but those that have concentrated on ecological rather than evolutionary considerations.