Wednesday, June 11, 2008

Heredity and Hope by Ruth Schwartz Cowan   posted by Herrick @ 6/11/2008 05:00:00 PM

The subtitle, The Case for Genetic Screening, seems to say it all. But Cowan comes at the topic as an historian with an interest in medical ethics. Here's how she makes her case:

1. She shows that historically the folks who came up with eugenics were different from the folks who came up with genetic screening. She is aware of the possibility of genetic fallacy, but I think she knows that people like it when their ideas flow from pure springs. She focuses on Tay-Sachs, beta-thalassemia, sickle-cell anemia, and PKU, showing that with the partial exception of sickle-cell, the drive for genetic testing came from parents whose children suffered from genetic diseases and from communities at high risk for the genetic disease. Thus, genetic screening is a bottom-up social phenomenon, not a top-down mandate. For the beta-thalassemia chapter, she spent some time on Cyprus, where the disease is relatively common, and her on-the-ground knowledge shows.

2. She shows that from a population genetics point of view there's a big difference between eugenics and genetic screening. Eugenics, she says, is a system of encouraging the fit to bear more children and perhaps discouraging or preventing the unfit from bearing children. Eugenics thus promotes 'good genes' in the population, the literal translation of eugenics. Modern genetic screening, by contrast, makes it easier for those with bad genes to bear children for two reasons. First, screening lets people with deleterious recessives find partners without such recessives, so the recessive alleles still stay in the population. Second, screening makes couples who both have the same deleterious recessive allele more willing to bear children, since they know they can abort a homozygotic recessive fetus. She actually has some decent anecdotal data on the second point. Thus, she repeatedly emphasizes that genetic screening is simultaneously "anti-eugenic" and "pro-natalist."

3. She tells a lot of human-interest stories about important firsts in genetic screening, focusing on happy endings. Given the importance of the law of small numbers, this is probably a good idea, and it's a relatively painless way for her to show how science and medicine work in the real world.

The book is exceptionally well-written, and while her history of eugenics contains few surprises, her history of the successes and failures of genetic screening was quite gripping. She also covers the basics of Mendel from scratch, so feel free to hand the book to anyone who took high-school biology. Functionally, Cowan does the same thing for genetic screening that The New Republic did for tough-on-crime policies in the 80's and 90's: Cowan does some liberal hand-wringing while telling the reader that no, you're not becoming a Brownshirt if you agree to an amnio.....

Related: Heredity and Hope: The Case for Genetic Screening by Ruth Schwartz Cowan.