Natural selection

Comments invited on this first draft of bit of the humanism book. It would be easy to get some detail about the science wrong. Please offer corrections or suggestions, however minor...

Another popular argument for the existence of God is the teleological argument or argument from design. Arguments from design begin with the observation that the natural world, or items within it, appears to have certain remarkable features – such as order and purpose - and conclude that God is the only, or at least the best available, explanation of those features.

Perhaps the best-known argument from design is that presented by William Paley in his Natural Theology, published in 1802. Paley argues that, were one to find a complex object such as a watch lying on the ground, it would be unreasonable to suppose that the watch came to exist by chance, or that it had always existed in that form. Given the clear purpose of the watch – to tell the time - and its highly complex construction geared to fulfilling that purpose, it is reasonable to suppose the watch was fashioned by an intelligent being for that purpose. But if that is a reasonable conclusion to draw in the case of a watch, then surely it is reasonable to draw the same conclusion in the case of a work of nature such as the human eye, which also has a purpose for which it is intricately and exquisitely engineered. That intelligent designer, supposes Paley, is God.

That a biological organ such as the human eye must have some sort of designer was accepted by very many, including even the scientist Charles Darwin, up until the Darwin developed his own alternative explanation of the existence of the eye – a theory that explains how the eye might evolve gradually over many millions of years without the aid of any intelligence.

The mechanism Darwin realized could account for the gradual evolution of the eye is natural selection. When living organisms reproduce, their offspring may differ slightly in inheritable ways. Plant and animal breeders take advantage of these chance mutations to breed new strains. For example, a dog breeder might select from each generation of a dog those that are largest and least hairy, eventually producing a whole new breed of huge, bald dog.

Darwin’s great insight was to recognise that the natural environment in which organisms are located will, in effect, also select among offspring. Organisms with a chance mutation that enhances their ability to survive and reproduce in that environment will be more likely to pass that mutation on. Organisms with a mutation that reduces its chances of surviving and reproducing in that environment will be less likely to pass it on. And so, over a many generations organisms will gradually adapt to their environments. Under certain condition, a whole new species may emerge.

Darwin called this mechanism “natural selection”, contrasting it with the “artificial selection” used by dog and plant breeders. Unlike artificial selection, natural selection does not require an intelligent mind to guide the selection process towards a particular end. Selection is now taken care of entirely by blind, unthinking nature.

There is overwhelming fossil and other evidence that the human eye did, indeed evolve slowly and gradually over millions of years, beginning perhaps with the chance appearance a single light sensitive cell in an organism living many millions of years ago, and that natural selection is indeed the main mechanism that drove this process. Indeed, eyes provide such obvious survival value to organisms that they have evolved independently at least forty times.

The discovery of the mechanism of natural selection led Darwin to reject Paley’s argument from design. Darwin wrote:

The old argument of design in nature, as given by Paley, which formerly seemed to me so conclusive, fails, now that the law of natural selection has been discovered.[REF4]

While the development of Darwin’s theory of natural selection, and, later, the theory of genetics (including the theory of genetic drift, another mechanism driving the process of evolution), resulted in a decline in the popularity of arguments from design, such arguments have recently been making something of a come-back. Two popular, more recent variants of the argument from design are outlined below.

Does the concept of an intelligent designer make sense?

Human beings explain features of the world around them in two main ways. One way is to supply naturalistic explanations that appeal to features of the natural world, such as natural events, forces and laws. The explanations of physics and chemistry fall into this category. The other way is to offer intentional explanations – explanations that appeal to the beliefs and desires of more or less rational agents. Why is there a tree in this spot? Because Ted wanted to see a tree from his bedroom window, and so planted a sapling here correctly supposing it would grow into a handsome tree.

When we are unable to explain something naturalistically, it is, of course, tempting to look for an intentional explanation instead. When we could not offer naturalistic explanations for why the heavenly bodies moved about as they did, we supposed that they must be, or must be moved by, agents - gods of some sort. When we could not otherwise explain diseases and natural disasters, we put them down to the actions of malevolent agents, such as witches and demons. When we could not provide naturalistic explanations for the growth of plants and the cycle of the seasons, we again invoked agents – sprites, fairies, and gods of various sorts.

As our scientific understanding of the world has increased, the need to invoke witches, fairies, demons and other such agents to account for features of the natural world has diminished. However, when we ask: why does the natural world exist at all, and what explains why it has the fundamental laws does? such naturalistic explanations are not available. So an explanation in terms of the activity of some sort of transcendent agent might seem attractive.

But does such an explanation even make sense? Suppose I claim that there exists a non-spatial mountain. It’s a mountain – with a sharp summit flanked by valleys and steep crags. Only it is not located or extended in space at all. It does not have spatial dimensions. This mountain transcends our spatial world.

You might well ask me why I suppose there is any such mountain. And if I cannot give you good reasons, you will rightly be sceptical. But actually, isn’t there a rather more fundamental problem with my claim that such a mountain exists? Can’t we know, before we get to the question of whether there is any evidence for the existence of my non-spatial mountain, that there can be no such thing?

For the very idea of such a mountain makes no sense. My hypothetical mountain has a summit and valleys and steep cliffs, but these are all features that require spatial extension. A summit requires that one part of the mountain be higher than another. A valley must be lower than the surrounding terrain. The concepts of a mountain, summit, valleys, and so on are concepts that can only sensibly be applied within a spatial context. Strip that context away and we end up talking nonsense.

But if we now turn to the concept of a transcendent designer, does that make any more sense?

The concept of an agent has its home within a temporal setting. An agent is someone or thing that performs actions as a result of its various beliefs and desires. But actions are events that happen at particular moments in time. And beliefs and desires are psychological states that have a temporal duration.

Now when we suppose that the spatio-temporal universe was created by some sort of agent, we are presumably supposing it was designed by a non-temporal agent – an agent that does not (or at least did not then) exist in time. For there was not yet any time for the agent to exist in. But if desires are psychological states with temporal duration, how, then, could this agent possess the desire to create the universe? And how did it perform the act of creation if there was not yet any time in which actions might be performed? It is hard to see how talk of a non-temporal agent makes any more sense than talk of a non-spatial mountain.

We could sidestep these puzzles by supposing that God exists, and has always existed, in time. This provides God with the necessary temporal dimension in which he might possess the desire to produce a universe, draw up a design, and perform the act of creation But it raises a host of other bizarre questions, such as: why did God wait so long before creating the universe (presumably, if God did not himself have a beginning, an infinitely long time)? And what was he doing in the meantime?