Human ecology is the study of the interrelations that exist between individuals, populations, and the ecosystems of which they are a part, while seasonality has been defined as regular recurring intra-annual fluctuation of environments, and of the individuals and populations living in them. The appreciation of seasonality as a significant source of human variability has a considerable history, anthropologists in particular long having recognised the importance of season in the structuring of people's lives and of their work and ritual activities. However, it is only more recently that the effects of seasonality on a range of human functions and activities have been widely investigated.

The Society for the Study of Human Biology Symposium on Seasonality and Human Ecology, held on April 9–10, 1992 at the University of Cambridge, allowed the different ways in which seasonality influences human biology and behaviour to be examined in a systematic manner by human biologists, anthropologists, physiologists and nutritionists. The papers discussed at that meeting are published in this volume.

In the first contribution (Chapter 2), F.E. Johnston discusses the range of biological phenomena associated with seasonality and concludes that, as a species, humans are enormously responsive to the seasonal changes and environmental cycles that characterise their ecosystems. He argues that environmental seasonality is not so much a stress to which contemporary human populations must adapt, but rather a basic component of the ecosystems within which our ancestors evolved, one that has left its mark indelibly upon the makeup of our biology and behaviour.