Evolution by natural selection is the great unifying concept of biology, so much so that most biologists now feel that, without it, none of the phenomena they study really make sense. Richard Dawkins (1986) provides an excellent modern survey of the great explanatory power of what has come to be called ‘neo-Darwinism’. Natural selection, operating on random, inherited variation has, over the generations, shaped animals to match the environments in which they live. Sometimes adaptation has been achieved through genes, accumulated over many generations, biasing the development of behaviour directly into appropriate responses. In other cases, animals inherit only biases to respond adaptively to their immediate environment so as to acquire, individually, appropriate responses by learning. Much behaviour develops by a mingling of such processes. All through this book we have emphasized the adaptive role of behaviour in an animal's life and so the concepts of ‘evolution’ and ‘adaptation’ have been implicit in much of what has already been said. Now we look at them in more detail.
In fact, not just one but two of Tinbergen's four questions are about the evolution of behaviour. One of them, about ‘adaptiveness’, is about how behaviour that we see present-day animals doing helps them to survive and reproduce. The other, about phylogeny, is about the changes in behaviour that have taken place over evolutionary time.