Introduction

The past 150 years have witnessed a quiet revolution in human development that still sweeps across the globe today: children nearly everywhere are growing faster, reaching reproductive and physical maturity at earlier ages, and achieving larger adult sizes than perhaps ever in human history. Although, in biological terms, the recent secular trends to accelerated growth and maturation may be nearly as dramatic as the widespread reduction in infectious illness and death, their social, psychological, behavioral, and health implications remain poorly understood. Yet we could think of the great improvements in public health and nutrition that apparently underlie the secular trends as a massive intervention in human development with ramifying consequences, likely positive, possibly negative. Rather belatedly, the possibility that developmental factors play a role in the contemporary emergence of chronic morbidities such as obesity, hypertension, diabetes, and cancer (Ellison, Chapter 6; McGarvey, Chapter 8) is now being considered. Martorell and colleagues have shown that early differences in nutrition predict later differences not only in adult size but also parental competence (Rivera et al., 1995; Martorell et al., 1996). Barker and his co-workers have developed the notion of early metabolic programming, based on epidemiological studies in British samples that link birth and placental weights to later risk for metabolic and cardiovascular disorders (Barker, 1997a, b).