Shawker, Thomas H. Unlocking Your Genetic History: A Step-by-Step Guide to Discovering Your Family’s Medical and Genetic Heritage.

Nashville: Rutledge Hill Press, 2004. 305p., softcover. Index, illus. $19.99. ISBN 1-4016-0144-8.

This is the fifth in a new series of instructional volumes sponsored by the National Genealogical Society, and when I reviewed the first four in The Louisiana Genealogical Register, I was very impressed. The authors were well known and trustworthy and their treatment of old subjects (such as basic research principles) and not so old (setting up a genealogy web site) was generally quite well done. But this one is somewhat different.

The subject of “genetic genealogy” is still very much unknown territory to almost all of us, even the professionals. It’s not even a “social science,” so one has to acquire a certain amount of new background knowledge even before delving into it. This author is also less likely to be known to most genealogists outside his own specialty: He’s a medical doctor, a Section Chief at the National Institutes of Health — although he has also been president of the Prince George’s County Genealogical Society and chairs the NGS committee on Family Health and Heredity, so he certainly can’t be called a beginner. Personally, I’ve been “doing genealogy” since the 1960s, but my background is in history, library science, and archival management, with no training and very little experience in the life sciences. Over the past decade or so, I have read dozens of articles in all sorts of journals on the subject of applying recent breakthroughs in DNA-mapping to family lineages, but even though I have been intrigued by the possibilities, the result has generally been to confuse myself even further. I’m pleased to say that Shawker has supplied at least a partial antidote to my ignorance.

The first section lays out the reasons you need to know about your family’s health history, because “ignorance is not bliss.” This is especially true among Acadian families here in Louisiana, as in other geographically or culturally isolated populations (Ashkenazic Jews, Amish, Afrikaners, Pacific Islanders) which suffer from a predisposition to assorted diseases and conditions. He follows this with a primer on the nature and process of genetics that is very well written and easy to understand (even for me), with a full explanation of dominant and recessive traits. He includes plenty of case studies, too, from King George III and the Romanovs to Gilda Radner. Then comes a section on compiling a health history, drawing up a medical pedigree, interpreting the results, and being aware of the warning signs for various important and common genetic diseases.

The part of the book I read most closely is that which explains in great detail, with many examples and illustrations, how the Y-chromosome is passed on, unchanged, from father to son to grandson, and so on, through the male line, and how the mitochondrial DNA is likewise passed without change from mother to daughter to granddaughter. The famous Thomas Jefferson-Sally Hemmings case — which was conclusively resolved by a leading genealogist, be it noted, not an academic historian — provides a good example of how all this works, and how one can use deduction to track lineages that are a mix of males and females. Numerous charts and diagrams also increase one’s understanding. Shawker also lays out a strategy for developing a family association DNA project to determine the relationships between groups with identical surnames, and he repeatedly makes the point that no testing program can prove anything: It can only serve as another research tool in conjunction with more traditional genealogical methods.

Finally, the author addresses the ethical and legal issues inherent in genetic testing, whether for family research or to identify an inherited tendency to contract a disease, and includes a lengthy guide to other resources on the Internet — especially important in a fast-developing area like this. There’s an excellent bibliography, too. Shawker is that rare scientist who can write coherently for the layman and I can recommend this excellent work to any individual or library with an interest in genealogical methodology.

Published in: on 30 May 2011 at 5:03 am  Leave a Comment  
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