Life and Persistence

The problem of persistence or the robustness of living processes is generally considered to be of secondary importance compared to questions relating to the 'functionality' of living processes, especially those associated with the brain. Following on from the work of researchers such as Maturana and Varela, the aim of the work I am doing with Professor Patricia Carpenter is to demonstrate that the question of how life maintains its organization through time is central to a complete understanding of all living processes and consequentially central to our understanding of the brain. If we can define in precise terms how an organism, such as a bacterium, can maintain its complex level of organization, we may be better placed to understand how hearts, livers, and, indeed, how brains work.

In his book Hidden order: How adaptation builds complexity. Holland considers the human immune system, central nervous system, ecosystems... "Many other complex systems show coherence in the face of change. ...We can see, for instance, that the coherence and persistence of each system depends on extensive interactions, the aggregation of diverse elements, and adaptation or learning. ...Even though these complex systems differ in detail, the question of coherence under change is the central enigma for each. (John Holland (1995) pp.. 2-4).

In his book 'What is Life' Schrodinger proposed that life organization is maintained by extracting 'order' from the environment. He coined the phrase - 'Negative Entropy' to describe this (Schrodinger 72-80).

Research into the complex world of biological systems has only partially addressed a long standing problem - the problem of robustness. A creosote bush (example shown above) may live for over 11 thousand years. A simple prokaryotic bacterium may represent a continuous process of metabolism that has lasted at least 3 billion years. How dynamic living processes maintain their coherence through time within the context of environments which themselves are highly complex is a question that has intrigued many researchers from a diverse selection of disciplines.

The problem is further complicated for the following reason - many biological processes are considered to be functional - that is to say that whereas a simple prokaryotic bacterium may only be concerned with the problem of sustaining its metabolism, cells, and other complex living processes that form part of larger organisms, seem to have 'jobs' to do in addition to the basic problem of survival. The problem then, is to reconcile the concept of 'functionality' with the more basic problem of survival or robustness.

But, can't functions be robust? In certain circumstances, yes, but this is the exception rather than the rule. An example of a process that combines function with robustness is a bone - its function is to be both strong and durable. However, if we consider the diverse functionality of the brain it is not so easy to reconcile these two ideas. Indeed, the functioning of the brain is thought to involve symbols and/or representations. A symbol or representation has no physical properties of its own - it is only meaningful within the context of a logical schema. This schema is a set of rules that must be instantiated physically. However, the physical support for the schema has physical properties of its own; the question is -- how did evolution integrate the functional with the physical organization to achieve robustness in both domains?

A similar argument, in favor of focusing on the persistence of life as a way to understand living systems, has been made by Maturana and Varela (1980). They proposed that a living system consists of a network of processes of production (and transformation and destruction) that realize and regenerate the network that produced them. Maturana and Varela argued that by considering the persistence of organisms we may gain insight into the possible ontogenetic and evolutionary transformations of biological systems, rather than focusing on diversity and reproduction as starting points and hoping to account for its persistence at a later stage. We will return to Maturana and Varela's ideas later in this web site; for now, we note that while both approaches focus on the organizational persistence of living systems, the current theory differs in its proposal of a specific principle underlying that persistence, a principle that may reconcile life's dynamic complexity with the laws of thermodynamics.