The Hamilton-Williams view of evolution, which I outlined in Chapter 3, sees genes as having a unique role to play in evolutionary explanation. They are taken to govern the construction of organisms, and organisms and their behaviours are taken to be designed in their interests. Views that take other things to be units of selection – for example, memes or groups – claim that at least some features of organisms are designed to serve the interests of things other than genes. However, those latter theories are still focusing on adaptation, that is, they are still giving answers to the question: what is x designed for? Where they differ is on the claim that, in so far as a trait can be said to be designed at all, it can be said to be designed for the benefit of genes.

It is compatible with either the gene-selectionist view or its rivals that very many traits are not adaptations at all. If there are traits that are not adaptations then they cannot be explained as being for the benefit of selfish genes, selfish memes, groups, or anything else. They require a different kind of explanation. But we are used to hearing evolutionary theorists offering explanations of traits in terms of how those traits promote the replication of genes and, in a minority of cases, in terms of how they promote the propagation of memes or the continuation of the group.

It was perceived very early in the history of biology that living things have parts that are for things. Aristotle (arguably the founder of biology) fully appreciated it: “In dealing with respiration we must show that it takes place for such or such a final object; and we must also show that this and that part of the process is necessitated by this and that other stage of it” (On the Parts of Animals: Bk I, pt 1).

The English word “teleology” is derived from the Greek word “telos”, which may be translated as “purpose”. What does this mean when applied to living things? When we think about a spider building a web, or a squirrel gathering nuts, we cannot help but see purposefulness in these activities. The spider builds a web in order to catch flies; the squirrel gathers nuts in order to secure enough food for the winter. By contrast, we would not say that the acid eats away at the metal in order to bring about some end; the process merely has an end result, and that is all. When it comes to the activities of animals and plants, it seems much more natural to say that they are carried out in order to bring about some end. Why does this idea have such obvious appeal?

Analogies between human beings and other living things

One reason for the appeal may be because of apparent analogies between other living things and ourselves. We know that human beings’ activities are (at least very often) purposeful. Often it is pretty obvious why people are doing what they are doing; if someone is putting on a raincoat, she is presumably doing so in order to avoid getting wet. But when we look at the activities of animals (leaving plants aside for the moment), they seem to be doing things that we also do: they eat, sleep, fight, run away from danger and so on.

In the immediate aftermath of Darwin's work, the idea that the theory of evolution had ethical consequences became quite widespread. Perhaps what makes this idea appealing is the popular notion that the theory of evolution in some way displaces or supplants religion. Religion is, after all, often seen as the source of moral teachings. If the theory of evolution significantly weakens the case for religious beliefs then, it might be thought, it had better generate moral teachings of its own. The alternative might be to be left with no moral teachings at all. However, there are a great many philosophers who think that ethics does not in any way depend on religion for its justification. Many of the early attempts to derive ethical consequences from evolution seem, from today's perspective, misguided. But the idea that we can learn something about ethics from evolution has not gone away.

Fitness as a normative concept

Evolution provides an account of how it is that living things have parts that are purposeful, that are for something. A world of purely physical entities, devoid of life, would presumably also be a world devoid of purposes. Those who are committed to a purely physicalist view of the world, then, are seemingly also committed to the view that purposes came into the world by means of evolution. Evolution explains why hearts, eyes and so on are for something.

As I mentioned in Chapter 8, the creators of the admirable Tree of Life internet project have not bothered with ranking terms such as phylum, class and so on. That, in my view, is one of the reasons why it is admirable. However, they do retain the ranking term “species”. Why do biologists who think that it does not matter whether a group is a phylum or not think it does matter whether a group is a species or not?

The word “species” has a historic resonance. Entities of all kinds fall into nested categories: gold is a metal and a chemical element; “3” is a natural number, an integer, a rational number and a real number. (Admittedly, the chemical tree is nowhere near as profuse as the tree of life; there are only a hundred-odd elements after all.) It would be correct to say that you are a human, a primate, a mammal, a tetrapod, a chordate, a deuterostome, an animal, a eukaryote and a living thing. (I have left out some categories in between.) But, by longstanding tradition, when we say what species something belongs to, we are saying what it is. Aristotelian essences are connected differently to species than to other levels of classification. For Aristotle, to say what species something is, is to give its essence: “essence will only belong to species of a genus, and to nothing else” (Metaphysics Z, 1030a13).

What often nowadays goes under the name “Darwin's theory of evolution” is in some ways different from Darwin's actual view. However, present-day evolutionists readily acknowledge that Darwin made the crucial breakthrough. In this chapter I want to show why that is.

Popular and polemical Darwinian literature often contrasts the theory of evolution with religious accounts of the origin of life, that is, with the claim that God is needed to explain the origin of life (e.g. Dawkins 1986). However, it is not at all obvious that the only alternative to Darwinism, as an account of why living things are the way they are, is that God created them that way. More sophisticated defences of Darwinism (e.g. Dennett 1995), sometimes contrast it not only with religious accounts, but with something that they refer to as “essentialism”. As this literature presents it, essentialism is, roughly speaking, the view that natural kinds – including biological species – can be given strict definitions, and are fixed and unchanging. It is true that Darwin perceived his assertion that species are not immutable as a major leap in thought: “At last gleams of light have come, and I am almost convinced (quite contrary to the opinion I started with) that species are not (it is like confessing a murder) immutable” (letter to Hooker, 11 January 1844, in Darwin & Seward 1903: 29). But in fact, as he was fully aware, he was not the first person to take this step.

The Hamilton-Williams theory of evolution focuses on genes as the “beneficiaries” of natural selection. It is alleged that genes, and genes alone, fulfil the necessary condition of having high enough copying fidelity. But natural selection is a substrate-neutral template, that is, it could in principle apply to any entity that fulfilled Darwin's necessary conditions of heredity, variation, population growth and limited resources. For all that I have said so far, there is nothing special about DNA that makes it alone the only thing that could be the locus of natural selection. Moreover, the move from Darwin's own organism-centred view to the gene-centred view of the 1970s was generally perceived to preserve a fundamental core of Darwin's theory as the same substrate-neutral template was still being employed. “Pure” gene selectionists are only claiming that as a matter of empirical fact, DNA is the only thing with the required high copying fidelity, not that it is the only thing that in principle could have it. Dawkins himself says that life on any other planet would have to have come about by natural selection, even though it might have a very different chemical basis from life on earth (Dawkins 1983).

Not everyone accepts the gene selectionists' claim about the uniqueness of genes. There are dissenting views over what can be said to be inherited, what it is that natural selection acts on, and what it is that is benefited when natural selection produces traits.

As I pointed out in the Introduction, philosophers of science have often concentrated their attention on the physical sciences. Often, indeed, the physical sciences have been taken to be examples of what a good science should be. For example, Popper illustrated his falsificationist criterion for separating the scientific sheep from the pseudo-scientific goats by taking Einstein's theory of relativity as a clear example of a sheep. One feature that is often held to distinguish the physical sciences is their possession of strict, exceptionless, mathematical laws (or, as some prefer to call them, simply “laws”). The speed of light is a strict mathematical constant, and the atomic numbers of chemical elements are exact numerical values. Sciences that lack such laws, such as meteorology or economics, are often relegated to the inferior status of “special sciences”. The main focus of this chapter will be on the features of biology that make it different from the allegedly exemplary physical sciences. Recall my earlier quotation from Dawkins to the effect that biology is a more unified science than physics. I shall argue that, when we examine what the unifying feature actually is, we can see that biology is more than a “special science”. In some ways it is exemplary.

Lawlessness in biology

There is reason to think that, like the special sciences mentioned above, biology does not have strict mathematical laws of its own. Th ere are, as in any science, generalizations. But these generalizations have a habit of proving to be: (i) not distinctive to biology; (ii) not strict, exceptionless, mathematical laws; or (iii) not laws at all. That is, put in more positive terms, the generalizations found in biology are: (i) laws that belong to other sciences; (ii) ceteris paribus laws; or (iii) true by definition.

The theory of evolution is often taken to be a triumph for naturalistic conceptions of the world. That is, it is often taken as a powerful vindication of the view that there is nothing that, in principle, cannot be explained naturalistically using the resources of the empirical sciences. Part of the general programme of many naturalistic philosophers is to replace traditional philosophical questions with scientific ones. This approach to philosophy was explicitly endorsed by John Dewey and W. V. Quine, both of whom have proved to be extremely influential in this regard. The questions of epistemology, such as “What is knowledge?” and “What can we know?” are among these traditional philosophical questions. There are two ways in which we might try to accommodate philosophy to a naturalistic worldview:

1. • It can be held that instead of asking purely conceptual questions, such as “What is knowledge?”, we should ask only empirical questions, such as “How, in fact, do human beings come to have the beliefs they have?” This approach, however, may be considered to be sidestepping the questions of traditional epistemology, rather than using science to help answer them.

2. • There is a more modest way of going about things. Whatever answer we give to questions such as “What can we know?” or “How is it possible that we can have knowledge?” had better be compatible with what our best current science tells us about what capacities human beings have.

3. […]

In the 1970s, a new consensus emerged among evolutionists, inspired by the work of William Hamilton (1964a,b) and George Williams (1966), and ably defended and popularized by Dawkins in his book The Selfish Gene ([1976] 1989). This view retains many of the essential features of Darwin's own view as outlined in Chapter 1, and retains both the aspiration to eliminate intelligent design from the explanation of biological traits, and the claim to have successfully done so. The orthodoxy of the 1970s has two central pillars:

1. • Gene selectionism (or gene centrism). It holds that, in so far as the traits of organisms are designed by evolution, they are designed, not necessarily so as to benefit the organism, but so as to benefit genes.

2. • Adaptationism. It sees natural selection as the primary force driving the modification of traits, and therefore as the primary tool of evolutionary explanation of traits.

The former marks a departure from Darwin's own view; the latter is claimed by some to do so. Of course, what matters is not whether these views are faithful to Darwin, but whether they are true. The Hamilton-Williams view is what many people know as “the theory of evolution” from popular science and media sources. It has, apparently, become difficult for many people to conceive that there could be alternatives to this version of evolutionary theory, other than religious or crackpot-science ones.

Much of the current public interest in evolution stems from the implications it has, or is alleged to have, for human nature. Darwin was aware of the possibility that it might have such implications: “In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation. Light will be thrown on the origin of man and his history” ([1859] 1968: 458).

He took some steps in this direction himself with The Expression of the Emotions in Man and Animals (1872). Moreover, Freud attempted to give his work on the origins of religion and morals a Darwinian underpinning. Implausible though Freud's theories in this area seem today, one recent commentator has called Freud the “first evolutionary psychologist” (LeCroy 2000). In the mid-twentieth century, the idea that human beings have species-typical, evolved, “innate” mental characteristics fell out of favour in many quarters. This fall from favour was due to the influence of a number of different schools of thought, including Marxism, behaviourist psychology and the Margaret Mead school of anthropology. However, the evolutionary approach to psychology never completely disappeared. One of its manifestations was Desmond Morris's bestselling book The Naked Ape (1967). Along with Morris's many subsequent books, it must take much of the credit (or blame) for fuelling the enormous public interest that has since developed in evolutionary approaches to human nature.

When I was at primary school, the teacher set my class an exercise of classifying a miscellaneous collection of objects into “alive”, “dead” and “never alive”. The second group included objects made of wood, paper and leather, and the third included ones made of metal and stone. Even at that early age – we must have been about six at the time – there was no perceived problem in assigning the objects to their various categories. Seeing things as living or non-living seems to be a basic component of our experience. We somehow have a gut feeling that there is an absolute difference between living things and non-living things.

The theory of evolution, however, rides roughshod over this gut feeling. For it leads to the conclusion that the processes going on in living things, and the processes by which they are created, are fundamentally the same as the processes going on in the non-living physical world.

Philosophy of biology can be considered a part of philosophy of science. Very broadly, we might say that philosophy of science deals with questions that arise from science, but are not themselves scientific questions. But this statement needs to be qualified. First, philosophy of science is not the same as history of science or sociology of science, both current growth areas. Nor is it, much, concerned with the ethical questions that arise because of science.