Human ecology: survival and disease patterns

THE LANCET • Vol 359 • March 30, 2002 • www.thelancet.com 1145 Changes in patterns of health, disease, and survival within populations over time indicate the interplay between human biology, culture, and environmental conditions. However, most epidemiological research, done within a particular population, focuses on identification of individual-level risk factors that operate in the foreground and with some immediacy. We pay rather scant attention to larger-scale factors that affect health at the population level and, often, over a longer time-frame. This more macroscopic perspective has increasing relevance for three inter-related reasons. First, we face rapid social and economic changes as the processes of globalisation and urbanisation occur. Second, we have begun to induce unprecedented large-scale environmental changes, including changes in the world’s atmosphere and climate, stocks of biodiversity, freshwater supplies, and food-producing ecosystems. Third, the international discourse on sustainable development is gathering momentum, and an understanding of the likely consequences for human wellbeing and health should be central to this debate about the attainment of an ecologically sustainable future. There has been a succession of profound transitions in human ecology over the centuries, especially in food production, social structures, urban living, reproductive behaviour, and demographic profile. The career of Homo sapiens has now reached an important juncture, at a global scale, that obliges us to assess the likely health effects for a population of today’s large-scale transformations in the conditions of living. Meanwhile, of course, variations in personal behaviours and exposures—in cigarette smoking, oral contraceptive use, dietary habits, workplace conditions, and so on—remain important determinants of health differences between categories of individuals within a population. But such differences, which arise at the individual level, comprise only one part—albeit an immediate and intuitively persuasive part—of a much larger story.