Philosophy of Biology

Brian Garvey

• Publisher: Routledge
• Year: 2014
• Print ISBN:
  9781844650705
• eBook ISBN:
  9781317493662
• Topic: Philosophy
• Subtopic: Epistemology in Philosophy

This major new series in the philosophy of science aims to provide a new generation of textbooks for the subject. The series will not only offer fresh treatments of core topics in the theory and methodology of scientific knowledge, but also introductions to newer areas of the discipline. Furthermore, the series will cover topics in current science that raise significant foundational issues both for scientific theory and for philosophy more generally. Biology raises distinct questions of its own not only for philosophy of science, but for metaphysics, epistemology and ethics. This comprehensive new textbook for a rapidly growing field of study provides students new to the subject with an up-to-date presentation of the key philosophical issues. Care is taken throughout to keep the technicalities accessible to the non-biologist but without sacrificing the philosophical subtleties. The first part of the book covers the philosophical challenges posed by evolution and evolutionary biology, beginning with Darwin's central argument in the Origin of the Species. Individual chapters cover natural selection, the selfish gene, alternative units of selection, developmental systems theory, adaptionism and issues in macroevolution. The second part of the book examines philosophical questions arising in connection with biological traits, function, nature and nurture, and biological kinds. The third part of the book examines metaphysical questions, biology's relation with the traditional concerns of philosophy of science, and how evolution has been introduced into epistemological debates. The final part considers the relevance of biology to questions about ethics, religion and human nature.

1. The argument in Darwin’s Origin

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.¹ 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. Among others, Jean-Baptiste Lamarck (whom I shall discuss briefly here) and Robert Chambers, in his anonymously published Vestiges of the Natural History of Creation (1844), took it before him. But that means that Darwin was not the first person to propose a theory of evolution. Why, then, is he regarded as one of the greatest scientists of all time, when Lamarck, Chambers and the rest are not? Darwin’s account of evolution, as I shall show in this chapter, is a successful account. Unlike earlier evolutionists, Darwin was able to show that the factors that produce evolution actually exist, and are sufficient to explain what he called on them to explain. For the purposes of demonstrating this, I shall very briefly present two earlier accounts of how life got to be the way it is. These accounts are not religious or “essentialist”, but attempt to explain things in terms of purely physical processes.²

1.1 Earlier attempts

First, a brief word on what Darwin called on those factors to explain. Ever since Aristotle, biologists had been aware of two salient facts about living things in general: teleology and taxonomy. Teleology (from the Greek telos, meaning “purpose”) refers to the fact that living things are organized into parts that look as though they were designed for a task. Our eyes are very good at seeing, and our hearts are very good at pumping blood around our bodies. Moreover, both our eyes and our hearts help us to stay alive, that is, they serve the living organism as a whole. It is not surprising that facts such as these have led people to believe that there just has to be a God: that they shout out “intelligent design”. One might alternatively think that organisms being that way is just a part of the way things are: it does not require any special explanation.³ Even before Darwin, however, there were people who would not accept either of these things.

Taxonomy (from the Greek taxis, meaning “order” or “arrangement”) refers to the fact that organisms fall into what appear to be reasonably well-defined classes or categories. Moreover, the categories seem to be nested: sheep and wolves are both mammals; mammals and fish are both animals; and so on. Again, one might see this as evidence of God’s design, or think that it is just the way things are. Again, not everyone was willing to accept either of these.

The germ of Darwin’s idea can be found in ancient times, particularly in the writings of Lucretius in the first century BCE. Lucretius was a member of the Epicurean school of philosophers, which means that his views were in some ways similar to modern-day materialists. Like them, he seems to have wanted to explain how animals are apparently well designed without appealing to an intelligent, deliberate designer. What he proposed was that nature initially produced all kinds of creatures: with wings, without wings, without mouths or any means of feeding themselves, and so on. Some of these simply died because they were ill equipped, while the better-equipped ones survived:

And in the ages after monsters died,
Perforce there perished many a stock, unable
By propagation to forge a progeny.
For whatsoever creatures thou beholdest
Breathing the breath of life, the same have been

Even from their earliest age preserved alive
By cunning, or by valour, or at least

By speed of foot or wing.

(On the Nature of Things: V)

This might seem to go some way towards an explanation of how creatures come to be well equipped for life. If we want an account of how we get organisms that are apparently designed, without having to invoke an intelligent designer, then Lucretius’s story has something going for it. The initial process that produces organisms does not have to be in any way geared to producing ones that are well designed. We should not be surprised that the ones that survived bear the appearance of good design.

It is, however, unsatisfactory on at least one important count. It requires us to believe that, at some time in the past, nature just spontaneously produced large numbers of creatures of various different kinds, completely at random. But we do not see this happening anywhere in the world now. We have never seen nature produce an organism, even a badly designed one, out of non-living matter. Did it do so once, and has it now stopped? Perhaps, but we have absolutely no reason to believe that this ever actually happened. By contrast, as we shall see, the factors that Darwin uses to explain things are processes that we can see happening in the world. Lucretius’s theory is thus speculative in a way that Darwin’s is not.

One of Darwin’s most famous immediate predecessors was Jean-Baptiste Lamarck. Nowadays, Darwin’s theory is often contrasted with Lamarck’s, but why is Darwin’s theory successful and Lamarck’s not? Lamarck’s name is preserved in the term “Lamarckian inheritance”, which is generally used to mean “inheritance of acquired traits”. This usage suggests that the difference between Darwin’s and Lamarck’s theories is that Darwin did not believe in inheritance of acquired traits. This, however, can be shown to be false by his assertion in On the Origin of Species: “I think there can be little doubt that use in our domestic animals strengthens and enlarges certain parts, and disuse diminishes them; and that such modifications are inherited” ([1859] 1968: 175).

The real difference between Darwin and Lamarck on this score is the use to which each puts the principle of inheritance of acquired traits in his theory. For Lamarck, it is the primary factor that explains how organisms come to be well designed for living in their environments. To use the example for which Lamarck has become notorious, giraffes’ necks are said by him to be so long because, in the past, giraffes stretched to reach leaves higher up the trees, and their offspring then inherited their stretched necks. This idea can be given some plausibility if one thinks about the thick skin human beings are born with on the soles of our feet. As we all know, skin gets thicker from continuous friction; guitarists often have thickened skin on parts of their fingers, and violinists on the part of their neck where they rest the violin. We might think, then, that the skin on our ancestors’ soles got thicker from years of walking, and that we inherited thick-skinned soles as a result.

But a problem with Lamarck’s account is that creatures acquire many modifications as a result of the vicissitudes of their lives. Creatures sometimes lose an eye, but their offspring are not born one-eyed as a result. For Lamarck’s account to work, there would have to be a systematic bias in inheritance in favour of beneficial traits. It would have to be the case that only they, and not the harmful ones, were inherited; otherwise the harmful ones could accumulate just as much as the beneficial ones. Although Darwin thought that some acquired traits were inherited, he saw no evidence that there was such a bias. His own theory does not require any such bias. Moreover, it does not require inheritance of acquired traits at all, as he himself was aware. Most present-day biologists reject inheritance of acquired traits outright.

Note that Darwin’s criticism is not that Lamarck failed to provide a workable mechanism for how acquired traits might be inherited. As we shall see, Darwin was fully aware that he himself knew of no mechanism for inheritance, or for the production of variations. It was sufficient for his purposes that his theory appealed to factors that could be shown to really exist, even though he lacked an explanation for them. This is why his theory is successful where Lamarck’s is not.⁴

There are further differences between Lamarck and Darwin. Lamarck believed in an inherent tendency to progress and a role for “slow willing of animals”. That Darwin criticized Lamarck for this view does at least have textual support, albeit in private letters rather than published works. Immediately after Darwin’s statement about species not being immutable, he writes: “Heaven forfend me from Lamarck nonsense of a ‘tendency to progression,’ ‘adaptations from the slow willing of animals,’ etc.! But the conclusions I am led to are not widely different from his; though the means of change are wholly so” (letter to Hooker, 11 January 1844, in Darwin & Seward 1903: 29). Once again, Darwin saw no evidence that there was any such inherent tendency to progress, or that animals could, by “slow willing” influence the future direction of evolution. Because of these features, as well as the need for a bias in inheritance, Lamarck’s theory can be considered a disimprovement on Lucretius’s theory. Lucretius’s theory did not require that there be any inbuilt bias towards good design or progress. He could explain how completely unbiased, undirected processes could produce good design.

However, both Lucretius’s and Lamarck’s theories fall down in virtue of having to appeal to factors for which we have no evidence. Darwin’s theory succeeds by appealing to factors that we can see really exist.

1.2 Variation and inheritance

Darwin uses the first chapter of Origin to write about the variation of plants and animals under domestication. He describes the activities of cattle-breeders, dog-breeders, pigeon-fanciers⁵ and so on, noting how they are able to produce new varieties simply by allowing some individuals to breed and not others. If a dog-breeder wants to produce dogs that have longer legs, she proceeds by taking the longest-legged dogs she has and allowing them to breed, and then taking the longest-legged offspring of those and allowing them to breed and so on. This tried and trusted method, Darwin points out, has produced a wide variety of different kinds of dog, pigeon and so on. In fact, dogs come in so many different shapes and sizes that even expert breeders at the time thought that they must be descended from a number of different wild species, albeit possibly a much smaller number than the great number of different breeds that we have today.

Why, we might ask, does Darwin bother talking about artificially-bred animals? Surely, we might say, (i) Darwin is just telling us something we already know, and moreover (ii) breeders may have produced new varieties of dogs or pigeons, but these are merely new varieties of old species. How is this supposed to tell us anything about how species themselves originate? But the title of Darwin’s book is On the Origin of Species, not On the Origin of Varieties. Let us examine these two objections more closely.

• (i) There is a world of difference between already knowing something and seeing what it implies. As we shall see, most of the evidence Darwin offers in support of his theory consists of facts that are similarly obvious, or easily derivable from what is obvious. Darwin was careful to amass evidence to verify these facts. For example, he spent some time consulting with professional animal- and plant-breeders. This is good scientific practice, for what is obvious is not always true. The facts that form the basis of his justification for his theory are none of them very novel or surprising. By contrast, think of the following example. According to Einstein’s general theory of relativity, gravity acts on light, so that a ray of light bends when it passes close to an object with a large mass, such as the sun. According to Newton’s theory, light always travels in straight lines. Thus, the two theories make different predictions. To test the predictions, scientists had to wait for a solar eclipse, to see if the apparent position of stars near the sun in the sky was as Einstein’s theory predicted, or as Newton’s theory predicted. There was a solar eclipse in 1919, and a team led by the astronomer Arthur Eddington went to Africa to make the relevant observations. Einstein’s theory passed the test. Before Einstein developed his theory, nobody expected to find this effect. In that sense, Eddington’s discovery is surprising in a way that the empirical facts that Darwin presents about artificial selection are not, and were not even at the time. But empirical facts that are not very surprising are still empirical facts for all that.
• (ii) Darwin argues that whether something is a new species or merely a new variety is, in part at least, in the eye of the beholder:
  How many of those birds and insects in North America and Europe, which differ very slightly from each other, have been ranked by one eminent naturalist as undoubted species, and by others as varieties, or, as they are often called, geographical races! Many years ago, when comparing, and seeing others compare, the birds from the separate islands of the Galapagos Archipelago, both one with another, and with those from the American mainland, I was much struck how entirely vague and arbitrary is the distinction between species and varieties.

  ([1859] 1968: 104)
  Ultimately, what he wants to argue is that the transition from one species to another is always by tiny steps, gradually accumulated. The fact that it is not clear when we should say we have a new species, is to be used as a piece of evidence for this.
  Moreover, Darwin later sets out to show that natural selection is much more powerful than artificial selection. Later in this chapter I shall get on to how he argues for this, but for the moment I shall stick to what he intends to show by talking about artificial selection. The production of new varieties by artificial selection is made possible by two factors:
  • A great many traits possessed by parents are passed on with a high degree of reliability to offspring.
  • This, however, is only a high degree of reliability, not absolute reliability. Two parents may produce an offspring that (e.g.) has longer legs than either.

Note that both of these factors are required for artificial selection to work. If the first were not the case, there would be no assurance that choosing the long-legged individuals for breeding would be any more likely to produce the desired outcome than choosing the short-legged ones. Breeders want the animals and plants they produce to breed true. But if the second were not the case, the production of a new variety with longer legs than ever before would not be possible. The term “natural selection” is often used to include the process whereby the average (say) leg length in a population goes up from generation to generation, even if there are no individuals in the new generation with legs longer than the longest-legged individuals in the previous generation. But Darwin explicitly speaks of the production of novel forms by artificial selection, and he offers evidence from (among other things) the world of pigeon-fancying to support this. If one was not keeping a careful eye out, one might think that the traits of an offspring are simply a new combination of traits already possessed by its parents. However, Darwin appeals to the testimony of animal- and plant-breeders – whose job requires keeping a careful eye out for such things – to show that this is not always the case.

This raises the question: what explains these two factors? That is, (a) why do organisms by and large breed true and (b) why do novelties sometimes arise? Darwin has no answer to these questions.

As regards (a), the fact that we do not know how to explain it – or, at any rate, they did not know in Darwin’s day – should not deter us from affirming that true-breeding is a fact of life. We expect children to resemble their parents. Nowadays, it is usual to explain true-breeding by appeal to the high “copying fidelity’” of genes. Not everyone accepts this, however, and I shall tak...

Table of contents

• Cover
• Half Title
• Title
• Copyright
• Contents
• Acknowledgements
• Introduction
• 1. The argument in Darwin's Origin
• 2. The power of genes
• 3. Units of selection
• 4. Panglossianism and its discontents
• 5. The role of development
• 6. Nature and nurture
• 7. Function: "what it is for" versus "what it does"
• 8. Biological categories
• 9. Species and their special problems
• 10. Biology and philosophy of science
• 11. Evolution and epistemology
• 12. Evolution and religion
• 13. Evolution and human nature
• 14. Biology and ethics
• Notes
• Further reading
• Bibliography
• Index