On Fertile Ground: A Natural History of Human Reproduction (review)

On Fertile Ground begins with two starkly contrasting tales of childbirth, one in the African jungle of the Congo basin, the other in the urban jungle of the American Northeast. However, it is not simply the cultural and environmental context that distinguishes these stories. They also represent extremes in a biological continuum of human birth experiences. We first read of an Efe pygmy woman in the Congo who prematurely delivered twin sons following a brief labor. Both babies die. Surprisingly, it is their births, not their deaths, that trouble the woman and her community; folk wisdom recognizes that twin births are not the norm. In contrast, the birth of the author's son in a Boston hospital was successful after 24+ hours of labor, epidural pain relief for the mother, an attempt to assist the delivery using forceps, and finally a cesarean section, which was necessary because of pelvic-cephalic incompatibility. This birth illustrates the ability of medical technology to alter the process of natural selection. From this captivating foundation, the book develops as a narrative of the proximate (physiological) and ultimate (evolutionary) causes of the operational details of human reproductive physiology.

Ellison's premise is that selection on the reproductive system must be particularly strong because variation in reproductive function is often directly linked to variation in reproductive success (pp. 8–9). Ellison portrays the ovary as the central figure in the female reproductive system. The female gonad is attuned, he argues, to the energetic status of the mother such that ovulation is less likely when available energy is inadequate, thereby preventing the woman from becoming pregnant. Ellison not only explores how metabolism affects ovarian physiological function but also suggests why such responsiveness of the female reproductive system to energetics influenced the direction of human evolutionary history.

The concepts are illustrated by the review of numerous studies over the course of nine chapters, each written to direct the reader's attention to a particular phase or component of the human reproductive life cycle. Each chapter is punctuated with select black-and-white photographs that evoke the human lives and experiences that Ellison seeks to explain, and this contributes to the appealing presentation of the material. The level of detail with which reproductive physiology is explained makes this an excellent reference for anthropologists who ordinarily may limit their pursuit of reductionist explanations. Furthermore, this knowledge is essential to Ellison's ability to rephrase some of the most intriguing questions that have been raised in the field over the past decade, such as those regarding the evolution of menstruation and menopause. His approach is unusual and valuable because the proximate and ultimate causes of the reproductive phenomena under investigation are so well integrated.

In the first chapter, "Two Births," endocrine physiology is introduced. Ellison likens the action of hormones, molecular messengers, to a lock and key in order to describe how important the hormone receptors located on target tissues are to the effect of hormonal signals. Both protein [e.g., follicle stimulating hormone (FSH) and luteinizing hormone (LH)] and steroid hormones (e.g., estrogens, progestins, and androgens) figure prominently in the succeeding chapters, and the introduction to their function in the first chapter is useful.

In the second chapter, "Surviving the First Cut," the drama of fertilization and implantation of the conceptus in the uterine endometrium is reviewed. Here, Ellison directs our attention to the reasons that early pregnancy is so risky. For one thing, the mother's body mounts an immunological response to the conceptus, a foreign body. It is genetically distinct from the mother because of the presence of paternally derived genes. A second factor that influences the risk of early pregnancy loss is the quality of the endometrium. Therefore the cycle of growth, degeneration (including menstruation), and renewal of the human endometrium is explained in the context of implantation.

The chapter concludes with a review of two prominent papers on the evolution of menstruation originally published in...