The Origin of Life

Bright light


A number of mechanisms have been proposed to explain the maximum power principle.

I think the most important is the one originally articulated by Lotka in 1922. Most of the rest of this page is devoted to Lotka's idea - if you want to look at alternative theories, scroll right to the bottom.

Lotka's idea

Lotka noted the importance of energetic resources to survival - and noted:

[...] in the struggle for existence, the advantage must go to those whose energy capturing devices are the most efficient in directing available energy into channels favourable to the preservation of the species.

- Contribution to the energetics of evolution - Lotka, A. J., 1922

Lotka invoked natural selection - and claimed it would favour those who got to energy sources fastest and used them most "efficiently".

Something like this might explain the reason a maximum power principle applies in biology - but it is not obvious how it might apply to drainage patterns, turbulent fluid flow, and to other self-organising systems.

However, I think something very similar does apply to other self-organising systems.

Many self-organising systems exhibit a crude analog of the evolutionary process.

In particular the exhibit structures which exhibit varying degrees of permanence.

Some of these structures are better able to persist than other ones. Those structures most able to persist do so, while other structures with less staying power tend to vanish.

The result is that at any time when you observe the system there's a tendencey to observe the more stable, long lived objects, those that are good at persisting.

As you can see, there's an analogy with natural selection here - everything above also applies to biological systems.

As in the case of biology, the stable structures in self- organising systems need a flow of energy in order to maintain their structural integrity, and - since resources are limited, they tend to compete with one another for those resources.

I will next give some examples of non-living systems that nontheless exhibit this sort of selective process.

In the case of crystal growth, the objects that are good at persistence tend to be larger crystals. Small crystals often tend not to last for so long - because they are more likely to dissolve completely when the level of saturation in the liquid fluctuates. There are circumstances under which large crystals can be selectively favoured - while the smaller crystals tend to have the atoms sucked out of them.

Turbulent fluid flow shows a similar phenomenon - again with large vortexes tending to be favoured. If two vortices form in the same region, the result tends to be unstable - of of the vortices is inevitably weaker than the other one, and the stronger vortex sucks resources out of the weaker one until it collapses. Large vortices can only coexist if they are far enough apart from each other to not compete with one another for resources.

Drainage patterns exhibit a similar effect. Rivers remember where in the landscape they are flowing. Streams compete with one another for resources. Successful streams become rivers, and gain more tributaries, a very simple sort of reproduction.

I think the similarities between these abiotic systems and the evolutionary process in biology are the main reason why the maximum power principle appears to apply to both sorts of system.

In both cases structures with varying degrees of persistence form; these are then subjected to selection - and whether the structures can maintain their integrty by making rapid use of environmental resources is an important factor in which ones survive.

Roderick Dewar

Roderick Dewar has provided an explanation for why dynamical systems far from equilibrium tend to maximise their rate of entropy gain.

Dewar approaches the subject from the perspective of physics - and attempts to derive a maximum entropy production principle from information theory.

His work suggests that rates of high entropy dissipation can be expected in far-from-equilibrium systems - since an overwhelmingly large number of possible microstates in the system are in the process of dissipating entropy rapidly.

Dewar's work is interesting - but his papers are challenging to understand and interpret.


Tim Tyler | Contact |