Professor Ellison has written the definitive book on the physiology and life history of a central pillar of human evolution; reproduction. Moreover, this book is unique in it's elegance and treatment of human reproduction. It melds three often elusive topics that beg to be integrated, evolutionary theory, life history theory, and physiology. As a biological anthropologist with expertise in evolutionary and life history theory, endocrinology, and field methods, Professor Ellison has skillfully woven these perspectives into a concise discussion of how human reproductive physiology responds to environmental challenges. Anthropologists and physiologists have often been at odds in explaining variation in human fertility resulting in frustrating discussions involving the false dichotomy between genes and environment. Ellison rejects these simplistic notions and masterfully outlines how human reproduction consists of an interplay between the genotype and environment, resulting in adaptations that involve graded physiologic responses to ecological challenges such as caloric deficiencies and energetic expenditure. Indeed, the ability of human reproductive physiology to respond to environmental challenges seems to have been a key adaptation during human evolution. 'On Fertile Ground' is the product of years of field and laboratory research by both Ellison and his colleagues, the ramifications of which include a reexamination of human physiological variation, the constraints and selection pressures that shaped human evolution, as well as a fresh perspective on the etiology of contemporary health issues such as breast cancer. The writing is superb and the illustrations are outstanding in their detail and clarity. 'On Fertile Ground' is an extremely valuable and important contribution to contemporary biological anthropology and evolutionary biology as a whole. Indeed, 'On Fertile Ground' will be required reading for undergraduate and graduate students studying reproductive ecology in the biological anthropology program at Yale University. Ellison's work is an extraordinary achievement!