I have wanted for a long time now to discuss a topic of great interest to me. Or rather (since I have already discussed it at length with those I know) to discuss this topic with a broader audience, and especially those who disagree with me. The topic I wish to discuss has been, for a very long time, a controversial one, and so before I come to the discussion itself, there are some definitions I wish to clarify.
Throughout this article I shall be referring to explanations. While there is a common sense definition, I shall do my best to remain as close as possible to the definition used by David Deutsch:
“Explanation: Statement about what is there, what it does, and how and why.”
I shall also be using a related definition, one that helps us to distinguish good from bad explanations:
"Good/bad explanation: An explanation that is hard/easy to vary while still accounting for what it purports to account for.”
These definitions, from Deutsch’s work The Beginning of Infinity will at least, I hope, give some common ground and help to avoid unnecessary misunderstandings. I will also state immediately the importance of criticism: examining explanations closely to see their faults. Before discussing the topic at hand, I will discuss what I believe to be a parallel of some sorts which may help to shed light on explanations in general.
Let us examine the explanations that have been given for the motions of heavenly bodies. While it is impossible to list all explanations that have been given, some number of them can be discussed. We will begin with the explanation that the sky as we see it is simply a cloth spread by a god. During the day, the sun moves along the underside of this cloth, illuminating us and the blue underside. At night, the sun moves above the cloth and shines through holes in that cloth: the light passing through these becomes the stars.
Is this a good explanation? By our definition, we must judge how hard it is to vary. The answer is that it is very easy to vary: the sheet could be replaced with a wooden backdrop, or the underside of a great ship, or any surface. The source of the stars could be varied to be loose threads which caught fire as the sun passed. So this is a bad explanation.
Worse, it is not any explanation at all: it does not explain, at all, why stars wheel in the sky or why some of these stars (the planets) do not move in the same way as the rest. So something more is needed.
The next explanation was that of celestial spheres. The earth was thought to be at the centre of a group of spheres; each sphere contained at least one heavenly body. The final sphere contained the ‘fixed stars’, those that do not change their position relative to each other as they move through the sky. Each of these spheres rotates independently, and so we see the different movement of heavenly bodies through the sky. While this explanation has some attraction, and has some common sense charm, we must criticise.
Is it a good explanation? Unfortunately, no: any two spheres can be swapped with each other, and as long as the speeds are changed appropriately it will continue to explain the same things. Unfortunately, it remained the accepted model for over a millennium.
As evidence of its easy changeability, one must consider first the Tychonian system, in which the earth is the centre of some spheres while the sun is the centre of others. By varying the explanation, the same thing is explained. Second, one must consider that even heliocentrism – the belief that the sun, not the earth, is the centre of the universe – did not spell an end for celestial spheres. Copernicus himself proposed a different set of celestial spheres, with the sun at their centres. The explanation was so easy to vary that it could adapt to almost anything; it was a truly bad explanation.
However, the work of scientists during the belief in the celestial spheres, among them Galileo, set the foundation for an explanation that could upend the celestial spheres – not by showing that their predictions were incorrect, or by proposing a different centre to the universe, but rather by showing that there was no need for them. I speak, of course, of Newton’s explanations.
To condense the work of Newton down into something as small as an article is impossible: commonly referred to as the Principia, it became the foundation for an entire field, still commonly referred to as Newtonian physics. However, for the sake of this article, only Newton’s laws are of highest importance. These can be paraphrased as follows:
1) An object experiencing no external force will always either be still, or moving in a straight line.
2) How fast something accelerates is determined by the force applied to it and its own mass: as the force increases, so does acceleration; as the mass increased, acceleration decreases.
3) Every action has an equal (in strength) and opposite (in direction) reaction.
Newton’s universal law of gravitation – that all objects with mass attract each other gravitationally – is best explained by Bill Bryson in A Short History of Nearly Everything:
“...every object in the universe exerts a tug on every other. It may not seem like it, but as you sit here now you are pulling everything around you—walls, ceiling, lamp, pet cat—toward you with your own little (indeed, very little) gravitational field. And these things are also pulling on you.”
Common sense shows, quite clearly, that this is wrong. But as we have seen from putting the earth at the centre of the universe, and myriad other bad explanations, common sense is often wrong. Rather than judge this on common sense, we must criticise.
Is it a good explanation? Let us try to vary it. Let us vary the first law, to state that objects with no external force do not move at all: this leads to a very quick collapse of the universe, since there is no momentum: generally the only force on objects would be gravity, and they would all come rushing to each other with little to stop them. For the sake of brevity I will not go through all the laws, but similar thought experiments could be done. This explanation is very hard to vary, making it a very good explanation.
It is also very good at predicting the motions of heavenly bodies. Kepler had derived laws for the motions of heavenly bodies empirically before Newton; Newton’s laws gave the same, and sometimes better, results based only on the explanation itself. Everything about it seemed exceptional. But not all good explanations are right explanations, as we shall see.
Newton’s universal law of gravitation proposes a force of gravity through which objects are attracted to each other: this explanation was hard to vary, and accurately predicted the motions of heavenly bodies, but another physicist, centuries later, would provide an explanation that showed that it didn’t even need to be there.
The problem with the force of gravity, as we began to understand many years later, was that of a force carrying particle. Physics identified four fundamental forces: electromagnetism, the strong nuclear force, the weak nuclear force, and gravitation. These all act over a distance, and the first three are all linked to a particle: a particle which carries the force. Gravitation, however, has never been linked to a particle. This criticism leads to one of two paths: search for the particle; or find a new explanation.
Whether for this reason or another, or whether as a benefit of a different goal, solving the problem of the gravitational force fell to Einstein. As the implications of the special theory of relativity began to sink in, it was understood that there was no need for this force. Rather, objects with mass bend space and time around them. Once this has occurred, there is no need for a force of gravitation: objects going in a straight line through curved space will invariably curve themselves, and will often orbit. This is for the same reason that an aeroplane flying in a straight line from Johannesburg to London will chart what appears to be a curve on the map: a straight line is curved as long as the space it moves through is curved.
By allowing space and time to be bent my massive objects, Einstein had solved to problem. But this was a new explanation: it would be unfair not to subject it to the same criticism we have with all the others.
How hard is it to vary? Immensely: just slightly modifying the amount by which mass curves space results in our planet, and all those we know, never forming: they would either spiral into the sun long before becoming planets, or rocket into space on their own momentum. So this is a very good explanation. But so was Newton’s. Why do we then favour this over the other?
The answer is simple. Relativity explains a phenomenon which Newton’s laws never can: why time is affected by gravity. Newton can surely be forgiven this oversight; it was impossible for any human to experience and measure such effects at the time. However, Global Positioning Satellites in geostationary orbit experience a weaker pull from the earth than we do, because they are further away. And, astoundingly, time passes differently for them: they have incredibly accurate timekeeping devices on board for the sake of their calculations, but no matter how accurate they are, they keep going out: they keep time perfectly, but time is different up there. Fortunately, corrective measures are put in place to keep them accurate enough for their calculations.
It is for this reason that we prefer the explanation of bent space-time: it better explains the observed phenomena. However, to think that work on these explanations is over is foolishness: we have only come so far in our understanding by finding new explanations, and imagining that what we have now is the best, and is definitely correct, is what stalled us at celestial spheres for so many centuries. We must continue to criticise, and find new and better explanations for the phenomena we see.
And it is now that I turn to the issue that I wish to discuss, and the issue I claimed to be so controversial: the theory of evolution. I will begin this section by immediately stating that I am not an evolutionary biologist, or any kind of biologist for that matter. However, I have read a fair amount about evolution, and part of my research is related to evolution. I will do my best to focus on those parts I do understand. I also welcome corrections to my understanding.
Second, I wish to make it clear that I am not here to ‘disprove’ evolution. Even if that will be done at some time, I don’t think I am the man to do it. But I have a mind, and so I am as qualified as anyone to criticise explanations. And evolution is nothing but an explanation by our definition.
The ‘theory of evolution’ is no single thing, just as there is no ‘theory of gravity’ – rather, there have many theories attempting to explain these phenomena. However, I will not focus on pre-Darwinian theories: I begin with the theory suggested in ‘On the Origin of Species’. While there were multiple editions which corrected some errors and added new knowledge, the theory as understood today states that the diversity of life as well as improvements within species of animals can be explained by two processes: random mutation of an animal’s genes; and non-random selection of fit individuals. The fitness referred to here can have many forms – strength, cunning, attractiveness, speed – but all of these forms contribute to a single thing: ability to mate. The more fit an individual is, the more likely it is to pass on its genes to offspring. In this way, it was believed that species would continually improve and change – they would evolve.
Is this a good explanation? We can try to vary it: by eliminating mutation, no change can ever occur in an individual; by eliminating selection, fit individuals would be no more likely to have offspring than unfit individuals; making selection random has the same problem; making mutation non-random does allow the theory to be varied without changing what it predicts.
However, making mutation non-random necessitates saying what is driving this non-random mutation. Since no known law of physics or biology could guide these evolutions, making mutation non-random is a very large change. As such, the explanation is hard to vary and is a good explanation. With the advent of neo-Darwinism (including its rejection of Lamarckism) the explanation has become better. But we saw earlier that not all good explanations are right, and we choose between two good theories based on how accurately they explain the world.
First, we see that evolution predicts a diverse range of species very different from each other, but also separate species which are very similar. That is what we see, so it explains that well. It predicts (implicitly) the extinction of species which do not adapt. This we also see. Looking to the present, the Lenski experiments show adaptation in action – and the only difference between ‘adaptation’ and ‘evolution’ is time and scale.
However, there is one major prediction that the explanation makes that has not been experienced: transitional fossils. While there are a handful of examples of such transitions, they are few and far between. If evolution occurs with small mutations being selected for over many generations, then the fossil record should be scattered with transitional fossils; it is not.
There have been explanations for this occurrence, chief among them punctuated equilibrium which claims that species generally undergo little genetic change; the changes that do occur, occur rapidly over brief periods. While this does explain the lack of transitional fossils, it is not good enough for two reasons: first, it does not give even a hint as to why these rapid changes occur and so is not an explanation as we define it. Worse, though: the Lenski experiments, which are really our only sign of evolution occurring, have adaptations forming over thousands of generations rather than quickly; this time would almost certainly be greater for larger organisms.
That is not to say that punctuated evolution is necessarily ‘wrong’, only that as it stands it is a poor explanation. That may change. There is a greater concern, and it should be a concern for anybody interested in evolution, and in finding the truth in general: the criticism that was so necessary to move forward in our understanding of how heavenly bodies moved is missing in evolutionary circles.
I do not mean to claim that all those who believe evolution are not critical; however, my experience is generally that criticism of evolution is avoided by those who believe it, whether it comes from themselves or others. In my experience, anyone who dares question is either mocked for apparent misunderstandings, or simply ignored. I fear – and it is truly a fear – that evolution is being protected religiously.
Part of the reason for the reluctance to let go of the celestial spheres of the universe was its ability to match a literal interpretation of the Bible: the addition of religion to the explanation made people more willing to hang onto it, even if it was a bad explanation. Any criticism was resisted. And I fear that this is happening with evolution.
The only way to avoid this is to criticise, and to accept criticism from others. No idea can be thought of as immune, no explanation infallible. And, having mentioned religion, I would be remiss if I didn’t mention that I believe the same process should be followed by all those who believe anything: what we believe is always an explanation; all explanations should be subject to criticism; criticism can lead to better explanation. This is no less true for religions.
There are many other explanations that shape the way we see out world; we would do well, with each of these, to be open to criticisms about them, and to be open to new explanations. It is only through this process that we can ever hope to glimpse the truth of how the universe works.
This article may have been controversial, and many people may have gut level reactions to it. However, I would like to welcome an intellectual discussion. I would much rather discuss than argue, and would much rather argue than butt heads. If all you can hope to do is the latter, then perhaps it is better if you do not comment.