16. Darwin's statement of the problem-the attacks upon his answer

The Joule and Faraday experiments make semantic issues clear. If we want to measure something, we must first clearly understand the terms used; their specific references; and their behaviours with respect to any associated terms. It may be “obvious” that the air in Joule’s experiment would expand when he released the stopcock, but he was a scientist. He wanted to know why: what was it that made air expand when subjected to such conditions? As a scientist, Joule sought the answer directly in the phenomenon before him.

Figure 15: The Helmholtz energy
 The Helmholtz energy

When Joule conducted his gas expansion experiment, thermodynamics was still in its infancy so he did not have the appropriate language to describe it. We now have the luxury of both the molecular theory and the second law of thermodynamics—the latter based upon the former—to assist us. We now know that the air expands because its entropy, an extensive variable, must increase. Its molecules engage in a rectilinear motion that allows them to travel increased distances between collisions, thus reducing the system’s pressure. But since their velocity remains the same, their temperature holds constant. Because of the increasing distances between collisions, and as illustrated in Figure 15, the molecules do expansion work through their “Helmholtz energy”. They have a mechanical mode of behaviour, and a microscopic scale that evidences it.

Joule could only hint at these issues. He was a pioneer. He did not have the luxury of entropy, molecules, or the pressure-volume interactions of the hidden mechanical modes of behaviour measured by any Helmholtz energy to assist him. Since the Helmholtz energy tracks the changes in volume, which are changes in the mechanical modes, we immediately know that molecules are involved. Not having that armoury of concepts, Joule thus referred to specific volume, implying that the air had rarefied. But as we would now put it, the mechanical mode had changed.

Darwin was also a pioneer. He was as exemplary a scientist as Joule. He presented the core of his very different ideas by saying:

I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection … But Natural Selection, we shall hereafter see, is a power incessantly ready for action …. (Darwin, 1869, p. 76).

Natural selection was therefore the “solution” to the “problem” Darwin had identified. He, also, did not have molecular modes of action or behaviour to assist him.

Natural selection might well be Darwin’s solution … but he presented his solution very differently from Joule. Darwin unfortunately gave no mathematical formulae, no logically rigorous proofs, and above all else, no way to quantify his assertions. His answer was therefore left susceptible to wanton and seismic semantic shifts. But because of the different way in which Joule’s answers were framed, his discoveries have benefitted from a massive increase in knowledge in a way that Darwin’s have not. Joule’s discoveries were therefore rendered immune to seismic epistemological shifts whereas Darwin’s have suffered them unendingly.

Only the first, and so perhaps the most influential, of the semantic shifts imposed on Darwin’s natural selection and competition doctrine came from Herbert Spencer with his highly evocative notion—long associated with Darwin—of ‘survival of the fittest’ (Spencer, 1864). Contemporary scientists may well prefer more neutral expressions as such as “high representation of gene frequencies in descendent gene pools” but those are only temporary disguises (Milner, 1990, p. 165). Discussion almost always returns to “fitness”, howsoever that is understood or interpreted by whatever protagonist has the floor at that moment.

The essential problem is that Darwin was unclear. The core essence of his idea has remained so. Therefore, he and his ideas have been left open to unending attack. Earl Hanson, in his book Understanding Evolution, neatly summarizes the reasons for these still unabated attacks upon Darwin:

Because the diversity of living things is so great, the ambition to explain it might seem ambitious. But that really depends on how we seek our explanation. Sticking to questions that science can answer, we find ourselves simply asking: What causes the diversity of the living things we see around us? And how we answer such questions in science can be outlined quite simply. …

… Darwin’s work followed the classic outlines of problem-solving in science. Initially, he defined the problem of organismic diversity. Then he looked for and found a solution. Darwin was not the first to try to explain organismic diversity, but he was the first to offer an explanation that lasted (Hanson, 1981, p. 35).

Those opposed to Darwin are opposed because they do not see a “problem” needing a “solution” in the first place. And since there is no problem, then Darwin’s supposed “solution”—so the opponents argue—is specious: it is an imaginary proposal directed at an equally imaginary problem. In their view, organismic diversity is already adequately accounted for “by other means”. Therefore, scientists should not even be addressing it. It is beyond the scientist’s purview.

As a scientist, Darwin adopted the same general strategy as his slightly younger contemporary, Joule. He directly observed his objects of study—in this case, biological organisms—and sought for the solution to the problem of diversity in the phenomena presented to him. That perspective adopted, Darwin identified the solution: those interactions in the environment that allow any variations amongst biological entities to express themselves down through the generations, and so over historical time. Those variations, he argued, will then lead to much wider and more significant differentiations through descent:

Let it be borne in mind how infinitely complex and close-fitting are the mutual relations of all organic beings to each other and to their physical conditions of life. Can it, then, be thought improbable, seeing that variations useful to man have undoubtedly occurred, that other variations useful in some way to each being in the great and complex battle of life, should sometimes occur in the course of thousands of generations? If such do occur, can we doubt (remembering that many more individuals are born than can possibly survive) that individuals having any advantage, however slight, over others, would have the best chance of surviving and of Procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed. This preservation of favourable variations and the rejection of injurious variations, I call Natural Selection. Variations neither useful nor injurious would not be affected by natural selection, and would be left a fluctuating element, as perhaps we see in the species called polymorphic (Darwin, 1869, p. 95).

There are, of course, several difficulties here. Darwin himself recognized them and did his best to deal with them in the clearest language that he could. Darwin’s proposal may well be that natural selection results from an interaction between biological organisms and their environment, but without rigorous mathematical formulae; and without their supporting quantificational validations; then but one of the essential difficulties—as Darwin himself knew—is also articulated by Hanson:

Prediction using the theory of natural selection, as formulated by Darwin, was and still is very difficult, since the most obvious experiments necessitate long stretches of time so that changes can accumulate and generate species differences. Darwin realized this and took a different approach. Sensing that natural selection is going on around us all the time, Darwin wanted to intercept the process as it occurs naturally. He wanted to be able to say, that if natural selection occurs, we should expect to see those phenomena that result from natural selection. …

Darwin discusses six major tests of natural selection. If natural selection occurs then we should expect to find:

  1. Some forms lose in the struggle for survival and become extinct.
  2. In small areas organisms will diverge as a result of the struggle for survival going on among them.
  3. Transitional forms, which are on the way to forming distinct species, will appear.
  4. New physical characters will emerge, including very complex ones, such as complex eyes.
  5. New behaviours or instincts, as Darwin called them, will also appear.
  6. Variations within species will be seen to be of the same sort as those that give rise to species themselves (Hanson, 1981).