The evolutionary path which living systems take is described as being contingent upon local environmental conditions.

While it is true that the events that take place as a consequence of evolution depend critically on the environment in which they occur, the conclusion that therefore the result does not have a directional character neglects the possibility that there may be systemactic regularities in the environment which effectively provide such a direction.

In fact in the natural world the environment is full of regularities. The spatial and temporal structure of the universe is characterised by large scale structure and regularity - and this does, in fact, result in a direction to the evolutionary process.

In particular, the biosphere is accumulating "natural technology" that helps it more rapidly identify sources of potential energy - and degrade them in the process of constructing offspring.

The accumulation is progressive, cumulative - and inexorable in character - and the resulting ratched mechanism provides evolution with a powerful progressive, directional character.

Some buddist scholars partition living systems into heaven, humans, fighting spirits, animals, ghosts and hell - on a kind of karmic ladder of rebirth.

Medieval scholars visualised the natural order in terms of the degree of perfection of organisms.

See the diagram of The Great Chain of Being on the right hand side. This illustrates a ladder from dirt, up through plants and animals, through people, on to angels and then up to god.

This picture sometimes gets criticised for failing to represent a cladistic tree - but that rather misses the point of what the picture is supposed to represent.

Though one can quibble about which organisms belong where, it turns out that the picture is just about right - when it comes to looking at evolution's directionality.

One thing it gets right is that it puts humans in a prominent position. From the point of view of the development of technological know-how, this is absoultely correct - it turns out that our own species is of pivotal importance.

Other thinkers have visualised much the same idea in other ways - e.g. the:

Geosphere -> Biosphere -> Infosphere -> Noosphere -> Omega point

...terminology - derived from the work of Teilhard de Chardin.

Technological setbacks are possible in principle. However the environment represented by the universe seems to be sufficiently life-friendly to mean that the probability of major setbacks is low.

Possible setbacks would include mass extinction events - perhaps caused by metorite impacts, seismic activity, sun storms, etc.

During such events whole classes of species may be obliterated - and their technology lost.

However much of life's most important technology has managed to survive such events. Often it has done so by finding its way into bacteria and single-celled organisms which can be relatively robust when it comes to mass-extinction events.

Certainly - in the history so far of life on this planet so far - the setbacks have been a retatively minor force in comparison with the progress that has been made - and many discoveries about ways of making a living have been successfully preserved for billions of years.

It appears that the universe is sufficiently life-friendly in at least one area for living systems to flourish and expand within it - allowing a technological ratcheting process to drive evolution forwards.

In a book on the subject [1], Gould claimed evolution lacked a progressive character - while Dawkins wrote in [a review of that book]:

Notwithstanding Gould's just scepticism over the tendency to label each era by its newest arrivals, there really is a good possibility that major innovations in embryological technique open up new vistas of evolutionary possibility and that these constitute genuinely progressive improvements (Dawkins 1989; Maynard Smith & Szathmary 1995). The origin of the chromosome, of the bounded cell, of organized meiosis, diploidy and sex, of the eucaryotic cell, of multicellularity, of gastrulation, of molluscan torsion, of segmentation - each of these may have constituted a watershed event in the history of life. Not just in the normal Darwinian sense of assisting individuals to survive and reproduce, but watershed in the sense of boosting evolution itself in ways that seem entitled to the label progressive. It may well be that after, say, the invention of multicellularity, or the invention of metamerism, evolution was never the same again. In this sense there may be a one-way ratchet of progressive innovation in evolution.

...and concluded:

For this reason over the long term, and because of the cumulative character of coevolutionary arms races over the shorter term, Gould's attempt to reduce all progress to a trivial, baseball-style artefact constitutes a surprising impoverishment, an uncharacteristic slight, an unwonted demeaning of the richness of evolutionary processes.

The view expressed here is similar to the one Dawkins expresses.

A drunkard's walk is a very poor and misleading metaphor for evolutionary progress. If you wanted to emphasise the random component of evolution, a far superior model is that of a gas expanding into a vacuum. However, such models are fundamentally impoverished - they miss out much of the interesting and important dynamics present in evolutionary processes.

Currently most of the niches that will be occupied in the future by large and complex organisms are all lying empty.

Living systems are expanding into these niches - very much like a gas expanding into a vacuum.

As with most explosive events, there's a clear direction: living systems are getting progressively better and better at identifying sources of energy and dissipating them - in the process of making copies of their genes.

Life is so much like an explosion that - while life still seems to have a single origin, our descendants will even be able to look back - and see an identifiable epicenter - with life's signature spreading radially outwards from it.

Few explosions retain their explosive character indefinitely. Eventually, they exhaust their available resources and slow down, fade and die. It may be that living systems will suffer the same fate.

However there's no sign that this is likely to happen any time soon - the living explosion shows every sign of continuing for many more billions of years - and building in intestity for a very long time to come.

Some argue that - in the case of evolution, this is not possible - since the mechanism of evolution works only on the basis of past experience, and can neither see nor predict the future.

However this is a feeble argument. All physics works on the basis of past events causing future ones - but that does not mean that systems which predict the future can't exist.

There are plenty of examples of prediction in nature. Weather forecasters regularly predict the future - despite the fact they all their knowledge stems from past experiences.

Since weather forecasters are part of nature, it seems clear that nature contains elements capable of predicting the future.

Organisms can not only predict the future, they can influence it. They can have plans and goals. The evolutionary process consists of a number of such individuals - and it effectively inherits the goals of the individuals that compose it.

So - the question can legitimately be asked - what is evolution's "goal" - what is it heading towards?

Life seems to be trying to occupy all space, and to become master of the universe.

More specifically, it is trying to maximise God's Utility Function/.

1. Full House: The Spread of Excellence from Plato to Darwin - Stephen Jay Gould.

2. The Phenomenon of Man - Teilhard de Chardin.