Psychobiology

The concept of evolution by natural selection has become the great unifying principle of biology, and before Darwin's "Origin of Species/* biology was little more than the accumulation of facts. For the past century the study of evolution has illuminated the past history and present state of every group of animals and plants. Darwin's theory required that selected adaptations be transmitted from one generation to the next, but he himself had little idea of how this was achieved. Following the rediscovery of Mendel's work early in this century, the basic mechanisms of heredity were rapidly revealed. These discoveries in their turn focused attention upon the nature of the genetic material itself, and now the remarkable developments in "molecular biology" over the past few years have almost completed the picture of the chemical basis of heredity.