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Description: Univ. of Oklahoma, Norman. Second volume in an unnamed series provides an interdisciplinary view of fertility and reproduction. Topics include anorexia as a reproductive disease, the evolutionary basis of menarche, the genetic basis of gender, twin fertility, and extramarital childbearing. For researchers and students.
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Review Summary: Review by American Journal of Human Reproduction &Fertility |
Date: 2004-05-05 |
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Details: Biodemography is a sullied concept in anthropology. It ought to be about the biological and evolutionary basis of demographic events that determine Darwinian fitness. Usually it is merely descriptive, and I have come to expect that titles with biodemography in them will disappoint. This book is a nice surprise: it has many pieces that do just what biodemography ought to do.
The strength of the book is that is it a collection of pieces (12 chapters) from different fields in anthropology, biology, epidemiology, psychology, and even sociology that are not obviously related and tempts scholars to read outside their fields. Anthropologists, for example, learn early on that phenotypic plasticity is what humans are about, and it never occurred to me to question the assumption that phenotypic plasticity is a good thing until I read the second chapter of the book, by Hughes, Burleson, and Rodd. Environmentally cued development may have costs not incurred by genes coding for canalized development. For example, there may be costs associated with information acquisition.
Most human reproductive ecology is based on plastic responses to the food supply or energy output, and we ought to be developing models that compare the costs of this kind of response to fixed responses. Valeggia and Ellison in Chapter 5 use Ellison's energy balance model (see Ellison, 2001) to interpret data on the duration of lactational amenorrhea in the Toba of Northern Argentina. Unfortunately, the beauty of Ellison's energy balance model is its weakness. It explains all the data we have or ever will have on ovarian suppression. In this sense it is not a true scientific model since it is impossibe to falsify.
The Toba have breastfeeding patterns similar to the !King Bushmen of Southern Africa. The !King are known for their long lactation periods and low fertility, and after Melvin Konner and Carol Worthman's landmark piece in 1980 establishing the intense lactation patterns of !Kung and suppressed ovarian activity, the 4-year-wide birth intervals of !Kung were attributed to lactational suppression. But the Toba have a surprisingly short period of lactational amerorrhea - half of all lactating Toba women have resumed cycling by 9 months postpartum, illustrating that breastfeeding intensity is not solely responsible for variation in lactational amenorrhea. Since there are no comparative data (Konner and Worthman's data were much less detailed), the piece does not elucidate the role of energetics, but Valeggia and Ellison describe some plausible physiological mechanisms for a regulatory role of food on ovarian activity.
Some variation in the timing of life history events previously attributed to plasticity can now be attributed to genetic variation. In Chapter 9 James Murray and colleagues describe differences in fertility among Honduran men with different alleles at the dopamine D2 receptor gene (DRD2)/TaqI/site. DRD2/Taq1/A1+ men have earlier age at reproduction and higher fertility than DRD2/Taq1/A1- men. In the past, they argue, the higher fertility of the DRD2/Taq1/A1+ allele was balanced by higher mortality in carriers that today produces excess morbidity. They summarize a large body of literature about genes with similar effects that may be responsible for so-called diseases of modernization (e.g., hypertension).
Like all edited volumes, this book varies in quality. Because the statistical methods and the theoretical content change with each chapter, the book is unlikely to be suitable for standard undergraduate courses. Undergraduates could grasp the conclusions, but not where they came from, and there are too many statistical techniques and too much theory and biology to introduce in a semester. Anderson and Low in Chapter 4, for example, find that the higher fertility of unmarried women disappears when covariates are included. This is an interesting but questionable finding. Many of the covariates (like age at first birth, age at marriage, and schooling) are competing risks. Women who become pregnant young are less likely to be married and receive less schooling, and a different model incorporating interactions among these terms might produce a different answer.
There are many other pieces by prominent scholars on many issues. This book should give readers a lot of new ideas with which to approach their own research problems, including up-to-date literature reviews in fields outside their own fields. It would be a great choice for a journal-club-like course in which students and faculty can hash out the issues and the consequences of better data or different statistical methods.
American Journal of Human Biology (Wiley-Liss), pages 101-102, Volume 16, Number 1 January/February 2004. |
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