Newspapers expanded around 1900 to reach a wider readership, often reporting sensationalized stories about science. Attacks on the Darwinian theory of natural selection intensified, leading to claims that the theory was on its deathbed. Lamarckism remained active along with the theory of directed variation (orthogenesis), both presented as less materialistic than Darwinism. New alternatives appeared, including the ‘mutation theory’ (evolution by jumps) and genetics, which was at first presented as a threat to Darwinism rather than a supporting factor. In the 1920s a new surge of creationism in the United States intensified the attack on Darwinian materialism, culminating in the widely reported trial of J. T. Scopes. The same critiques appeared in a less muted form in Britain. The Darwinian ‘struggle for existence’ remained a source of anxiety for those who feared a potential threat to moral values and social stability.

In the 1920s and 1930s the Darwinian selection theory was linked to genetics, providing it with a secure foundation, although wider dissemination of this initiative was limited until the 1940s. Historians note that the ‘evolutionary synthesis’ was a rhetorical device to create an impression of unity, leaving the various disciplines involved still functioning independently. Radio now became an important means of disseminating science news, as in the 1959 celebrations of the centenary of the Origin of Species. The new version of Darwinism eroded the plausibility of eugenics and race theory, although these ideologies remained active in less visible forms. Popular accounts of evolutionism now stressed its open-endedness and played down the old assumption that humanity must be the inevitable outcome of progress. Julian Huxley tried to give the synthesis a moral dimension by linking it to his philosophy of humanism, but creationists saw the new initiative in science as a continuation of Darwinian materialism and renewed their attacks.

Every textbook of biology will supply a number of ‘modes of speciation’, the ways in which new species evolve. But the issues in dispute among the biologists themselves are rather odd. The adoption of evolutionary theory by biologists has had a great impact on how species are understood. From the idea that kinds of living beings were created and at best had devolved to localised varieties, now species were the target of a ‘mechanical’ or ‘physiological’ explanation: they came into being. And under Darwin’s version of the evolutionary account (initially known as the ‘development theory’, since the Latin word evolutio means ‘development’), species were made from other, allied (which means ‘closely related’), species. The processes and causes of new species set up the ‘species question’ that Darwin and other naturalists were seeking to answer.

What are species worth? Do they have inherent value or are they just of value to human beings? Do they have rights? Does their integrity as species have moral worth, and do we have a duty to preserve them, or to modify them? Are species of utilitarian or instrumental value? These are the questions that the third great topic of philosophy seeks to answer: axiology – the values of things, and the duties they impose upon us as ethical, economic and aesthetic beings.

For a long time, species have been thought to be the index marker for healthy ecosystems, for undisturbed nature and for conservation, but the reasons why have varied considerably. National Parks developed from a desire to maintain potential sources of timber, game and hunting opportunities in the United States at the end of the nineteenth and the turn of the twentieth century, as demonstrated in Teddy Roosevelt’s book The Wilderness Hunter; An Account of the Big Game of the United States and Its Chase with Horse, Hound, and Rifle.

It’s not enough to just list the clusters in the living world. One also needs to group clusters together within larger clusters. This process is sometimes referred to as ‘ordering the world’, and is called taxonomy, from the Greek word for ‘order’, taxis. In traditional taxonomy, begun in the sixteenth and seventeenth centuries, and formalised in the eighteenth century by Carl Linnaeus, this meant that species were grouped together in groups called in Latin genera (that’s the plural; the singular is genus). As a result, Linnaeus gave each species a two-part name (a binomial): its genus name (which always has a capital initial) and its species ‘epithet’ (which is always in lowercase). So, our species binomial is Homo sapiens; we are the species sapiens in the genus Homo. It’s kind of like a street address – you have the ‘general’ name (the ‘street’) and the ‘specific’ name (the ‘house number’) (see Box 2.1)

There are several ‘enigmatic canid’ species in North America. One of them is the red wolf (Canis rufus, Figure 1.1), and another is the Great Lakes Wolf. Red wolves are seriously endangered, with a re-released population in North Carolina and breeding programmes being the last populations. Red wolves weren’t even studied closely until the 1960s, after having been hunted nearly to extinction in the nineteenth and twentieth centuries.

The title of this book is Understanding Species, and I have spoken at length about what we understand species to be and to mean. Now, though, I would like to ruminate for a bit on the ‘understanding’ part.

To understand something is not necessarily to have the One True Answer. Human knowledge, and especially its concepts, is in a state of flux at all times. Sometimes, this is because we are learning new things about what the concept refers to, as is the so-called rule in science (it sometimes isn’t). At other times it is because the concept no longer means anything (like ‘phlogiston’ in chemistry or ‘vital force’ in biology). But sometimes it is because the concept has been included into the ‘what everybody knows’ segment of culture. John Maynard Smith, a famous and influential British evolutionary biologist, called this the Bellman’s Theorem (from Lewis Carroll’s The Hunting of the Snark): ‘what I tell you three times is true’.

As I have noted, terms for species are at best polysemic (that is, they are a single word in a language with multiple and often incompatible meanings), and at worst species is a term with no meaning of any real scientific importance. Now we will consider several replacement concepts, and the evolutionary and genetic considerations that make them seemingly viable.

In Chapter 2 we considered the extent of the different definitions as applied to a simplified version of human evolution and genetics. One of those definitions included a historical aspect – monophyly.

If there is an issue in a science, philosophers will attend to it. This is not new, either. Since the rise of modern science in the seventeenth century, many if not most of the problems that philosophers have addressed or formulated have arisen out of science one way or another. Books on ‘the philosophy of botany’ or ‘the philosophy of natural history’ were published from the late eighteenth century onwards, although ‘philosophy’ meant knowledge in those days, and included scientific thinking. Nevertheless, science has always been a productive source of new problems for philosophy to chew on.

One of the things that is often said about the frankly catastrophic loss of biodiversity in the world today is that extinction is a natural process of the living world, and this is quite true. Extinction does not naturally occur at a constant rate, however. It ranges from near instantaneous (as when a 12-km-wide rock hits the planet, causing a Very Bad Day for most living things) to a slow background rate of extinction of species that have been reduced to a relic of past distributions and population numbers. So, when those who do not think we are in a catastrophic situation say, ‘Extinction is natural’, point out to them that the present scale of extinction is in global terms worse than a 12-km bolide, at least in geological terms, for the geological record doesn’t distinguish easily between a one-day catastrophe and a four-century one. Both are ‘sudden’ events in Deep Time. As E. O. Wilson wrote, in his book The Diversity of Life (1992)

There are, says Professor Julia Sigwart, an American mollusc specialist (malacologist), species makers and species users. The former are the taxonomists, and they identify, name and record species in technical journals and store the type specimens (the original specimen that ‘bears’ the name) in museums and other collections. There are way too few of these. The latter – well, that includes everybody, according to Sigwart. She notes in her 2019 book What Species Mean (chapter 3) that looking out of her window she sees species of tree, animal, bird and other living things, and that this knowledge involves two main steps: knowing that something is different from other similar (or related) things; and giving it a unique name to communicate and identify it to other users, for the taxonomists are also users of species. Knowing and naming species are related activities, but not the same.

Textbook histories are how most scientists learn about the past of the ideas and disciplines they employ, and any textbook will tell you that the idea of species goes back to the classical era if not earlier. In a way this is true, but textbook histories are written by scientists, not historians, and they often repeat untested or false ideas for reasons other than knowing the past. Often, history is something to be used as a way of establishing the in-groups and out-groups of science; in other words, history can be used as a weapon in the sciences. So, some critical revision is required.

Plato’s theory of Forms uses a closely related term ‘idea’ as well as eidos to denote ‘forms’, which are eternal and beyond the physical. Plato, as with philosophers since who are interested in kinds of things, used biological illustrations, such as ‘horse’, ‘human’ and ‘dog’, but he did not think actual horses, humans and dogs were species (or members of a class of things) because none of them, not even Socrates himself, were perfect examples of their forms.

This chapter provides an outline of Mendelian and molecular genetics, with a particular emphasis on how DNA provides evidence of a single origin for all living things. It discusses the role of genetics in serial homology, and how that demonstrates genetic relatedness among vertebrates especially, and it shows how homologous HOX genes provide the head–tail orientation and body plan segmentation for animals as diverse as the house fly and human, and that we see this same pattern of segmentation as far back as the Cambrian. It also explains how the independent DNA of mitochondria and chloroplasts provide evidence for a deep history of symbiosis between the host and parasite for both plants and animals. This chapter provides a support for later chapters reviewing principles of evolution and the evolutionary history of complex organisms.

This chapter investigates the critique of anthropomorphism that we find in Xenophanes of Colophon and Heraclitus of Ephesus. Hesiod’s Theogony is assumed as background and as paradigm for the tendency to treat either the world’s components or gods generally as humanlike. With Xenophanes of Colophon we have the first and one of the fiercest attacks on such a kind of anthropomorphism, inasmuch as Xenophanes not only challenges anthropomorphism in traditional religion and myth but also intimates that at the root of religious beliefs and practices, among his fellow Greeks as well as among foreigners, is a motive of philautia, of self-love. Another strong early critique of anthropomorphism is found in Heraclitus of Ephesus, who curtly dismisses the idea of world-making by a god and stridently attacks certain traditional forms of religious worship. And yet neither thinker can avoid sliding into a particular kind of anthropomorphism, namely into what Mourelatos calls ‘epistemic anthropo-philautia’ – philautia understood not as the ‘self-love’ or ‘vanity’ an individual may show, but rather as the species-philautia we indulge in when we project upon the cosmos structures and forms that cognitively afford special intuitive appeal to us human beings.

In modern creationism, blood-language (even more than a high view of scripture) determines whether evolution can be true. In One Blood, leading creationist Ken Ham finds evolution too bloody for a good God. A good God could hardly use predation, extinction, and death as a means. For Ham, blood sets humans at one with or apart from the “dumb beasts.” But Ham drafts too narrow an atonement, where the blood of Christ makes up only for sin. Blood must also mean solidarity. Uses Irenaeus, William Jennings Bryan, Marilyn Adams, Teilhard de Chardin, Sergei Bulgakov.

Chapter 2 examines how adaptive appearance could problematise Victorian natural theology through the example of the parson-naturalist Charles Kingsley. Kingsley’s faith was bound up with ideals of truth and sincerity, which he imagined as divine values that God’s creation exemplified and symbolised. Adaptive appearance challenged this textual view of nature, suggesting that nature’s aspects served purely to promote organisms’ survival, often through deceit. It is argued that Kingsley sometimes tried to resolve this contradiction by locating truthfulness in the rise of science instead of in raw, animal nature. In texts such as Glaucus: Wonders of the Shore and his evolutionary fairy tale The Water-Babies, he depicts science as a providential realisation of God’s values. However, Kingsley also sought to preserve vestiges of moral symbolism in nature since this notion underlay both his religious faith and the Church’s authority in knowledge of the natural world. Kingsley’s insistence on nature’s symbolism cohered with his insistence on the spirituality of the body, preserving a link between matter and divinity. This rhetorical strategy would be echoed by other religiously committed commentators who sought to reconcile adaptive appearance with the notion of nature as a divine text.

In 2005 I was invited to contribute to a volume celebrating the life and work of Richard Dawkins, which was published in 2006 under the title Richard Dawkins: How a Scientist Changed the Way We Think. My essay title plays on Richard’s 2003 anthology A Devil’s Chaplain: Reflections on Hope, Lies, Science, and Love. After decades of illuminating the minds of millions of people through his popular science writing, Richard Dawkins turned his keen mind to religion, and the result was the birth of the New Atheist movement, which began shortly after this tribute volume was published.

This article first appeared as a book chapter in the <italic>Handbook of Philosophy and Public Policy</italic>, edited by David Boonin and published by Palgrave in 2018. I was tasked with finding a test case of freedom of speech and inquiry from the sciences, in the larger context of free speech issues as related to public policy and the law. I have already written extensively about evolution and creationism, most notably in my 1997 book <italic>Why People Believe Weird Things</italic> and my 2006 book <italic>Why Darwin Matters</italic>, so here I engage the creationist movement as a free speech issue inasmuch as its proponents hold a minority viewpoint as far as the scientific community is concerned. Nevertheless, I contend that they should be free to believe, teach (and preach) whatever they like about the origins and diversity of life, and that, in the well-trodden principle, sunlight is the best disinfectant (to which Supreme Court Justice Louis Brandeis added “electric light the most efficient policeman”).