6. Genes

There is no satisfactory one-line answer to the question ‘what exactly is a gene?’. The reasons why a precise definition is elusive are particularly interesting, and raise a number of philosophical subtleties. ‘Genes’ delves briefly into the history of genetics in order to understand them. It first looks at the work of Gregor Mendel in the 1860s and then the era of classical genetics in the 1920s and 1930s. It then moves on to molecular genetics, which came to fruition in the 1950s. How does the gene of Mendelian or classical genetics relate to the gene of molecular genetics? This question has long occupied philosophers of biology.

4. Levels of selection

‘Levels of selection’ examines the levels-of-selection question, which asks whether natural selection acts on individuals, genes, or groups. This question is one of the most fundamental in evolutionary biology, and the subject of much controversy. Traditionally, biologists have mostly been concerned with selection and adaptation at the individual level. But, in theory, there are other possibilities, including selection on sub-individual units such as genes and cells, and on supra-individual units such as groups and colonies. Group selection, altruistic behaviour, kin selection, the gene-centric view of evolution, and the major transitions in evolution are all discussed.

3. Function and adaptation

A striking feature of the biological sciences is their frequent appeal to the notion of function. Why do biologists make such liberal use of function-talk, and what exactly does it mean? ‘Function and adaptation’ explores the concept of biological function and asks how it should be understood. There are two rival philosophical theories of function: the aetiological theory and the ‘causal role’ theory. The aetiological theory emphasizes that function attributions are often answers to the ultimate question ‘why does it exist?’ whereas the causal role theory draws attention to a proximate question, namely ‘how does it work?’.

2. Evolution and natural selection

In 1859 Charles Darwin published On the Origin of Species, in which he set out his theory of evolution. The book marked a turning point in our understanding of the natural world and revolutionized biology. ‘Evolution and natural selection’ outlines the theory of evolution by natural selection, explaining its unique status in biology and its philosophical significance. It considers how Darwin’s theory undermined the ‘argument from design’, a traditional philosophical argument for the existence of God; how the integration of Darwin’s theory with genetics, in the early 20th century, gave rise to neo-Darwinism; and why, despite evolutionary theory being a mainstay of modern biology, in society at large there is a marked reluctance to believe in evolution.

7. Human behaviour, mind, and culture

‘Human behaviour, mind, and culture’ examines the implications of biology for humans, asking whether human behaviour and culture can be explained in biological terms. The intelligence, language use, cultural inventions, technological prowess, and social institutions of our own species, Homo sapiens, seem to set us apart from other species. Can biology shed any light on humanity and its achievements? One way to tackle this question is to ask whether human behaviour can be understood in biological terms. The nature vs nurture debate is discussed, followed by the approaches of sociobiology and evolutionary psychology to the study of human behaviour. Finally, cultural evolution—or dual inheritance theory—is considered and how this relates to biological evolution.

1. Why philosophy of biology?

Philosophy has long been intertwined with the natural sciences. Many of the greatest philosophers of the last 400 years were influenced by the science of their day and some made important scientific contributions of their own. ‘Why philosophy of biology?’ explains that the birth of science gave rise to a new type of philosophical enquiry, which asks questions about the methods of science itself. Philosophy of biology emerged in the 1970s as a distinct field of enquiry from the interplay of three factors: the need for a less physics-centric picture of science; the presence of conceptual issues within biology itself; and the naturalistic turn in general philosophy.

5. Species and classification

‘Species and classification’ first considers the species problem and the biological species concept. It then discusses phylogenetic systematics, which involves the organization of species into higher taxa. Classification in science raises a deep philosophical issue as all objects can in principle be classified in more than one way. Is there a ‘correct’ way to assign organisms to species, and species to higher taxa? Classification of organisms was traditionally done using the Linnaean system, which served biologists well for years, and elements of it are still used today. However, the rise of evolutionary biology has led to fundamental changes in both the theory and practice of biological classification.