She Has Her Mother's Laugh The Story of Heredity, Its Past, Present and Future

If Charles Darwin were to walk into my office today and ask me: “So, what did I miss?” I think I would sit the good man down with a copy of She Has Her Mother’s Laugh, telling him: “Here, this should get you up to speed”. Darwin struggled to explain how traits were being inherited from generation to generation. As New York Times columnist Carl Zimmer shows in this wide-ranging book, the story of heredity has turned out to be both diverse and wonderful, but has also been misappropriated to prop up some horrible ideologies.

With the narrative itself sprawling over more than 570 pages, the scope of this book is vast. In the hands of a lesser writer, the prospect of reading such a large book on a technical topic such as heredity might seem daunting. Zimmer, however, is very adept at combining his personal experience as a father with the results from historical and current scientific research, frequently highlighting the many human stories and dramas leading to new findings.

Starting with our understanding of heredity before Darwin, Zimmer walks us through Darwin’s failed attempt at explaining heredity in The Variation of Animals and Plants under Domestication (see also Van Grouw’s recent celebration of that book in Unnatural Selection), the forgotten work of Mendel that was rediscovered decades later, and the “laughably baroque” cell division process of meiosis that results in egg and sperm cells. There is the obsession of many people with genealogy, something that received renewed interest with the falling costs of sequencing technology. Zimmer has his own DNA sequenced and uses this as a hook to talk about ancient DNA recovered from archaeological remains and how this has revealed that we are all complex mosaics of many different ethnic groups, with even some Neanderthal DNA thrown in for good measure! (see also Pääbo’s Neanderthal Man and my review of Reich’s excellent Who We Are and How We Got Here that goes into much more detail).

Mendel’s principle of inheritance is not the only mechanism though. Zimmer goes into the discovery of the complex inheritance of traits such as height and intelligence that rely on small contributions from many genes, the nature/nurture debate and what studies on human twins have revealed, or the astounding discoveries that our bodies are mosaics of genetic variation due to localised mutation, and that some people are even chimeras containing genetic material from more than two people.

The concept of heredity becomes even fuzzier once we start adding the discovery of the microbiome (the community of microbes that lives in and on us), epigenetics (heritable changes due to changes in gene activity rather than sequence), or the notion that culture is a form of heritability to pass on knowledge. You can see why Bonduriansky & Day are calling for a reappraisal of the concept of heredity in their recent book Extended Heredity.

But what of this misappropriation? Ah yes, the dark side. Throughout all these various chapters Zimmer weaves the troubled contribution mental institutes have made to our understanding of heredity (see Porter’s Genetics in the Madhouse), the subsequent rise of the eugenics movement that hoped to improve the human race through forced sterilization, the horrors of Nazi Germany, and the persistence of the outdated idea of race that for centuries has been used to justify slavery and racism (see Sussman’s strident takedown in The Myth of Race). Given his own Jewish background, his treatment of these topics is surprisingly dispassionate. Although he obviously opposes all of the above, his assertion that “it’s also a mistake to use Hitler as a label for all of eugenics” (p. 499) and his willingness to discuss Hermann Muller’s ideas on more progressive forms of eugenics shows Zimmer to be open-minded, or at least able to keep his writer’s cool.

This, of course, brings us to all the ethical quandaries stirred up by the discovery and application of CRISPR (see also my reviews of A Crack in Creation and Modern Prometheus). This new tool to edit genetic material has the ability to cure diseases but could also be used for more questionable ends such as designer babies. There are no simple answers here, and Zimmer gives a great overview of the debates and the rapid pace with which this technique is developing.

As you can see, I have been reading into quite a few of the topics that Zimmer deals with. Even so, the quality of his narrative, the well-placed humorous comparisons, and the human portraits he mixes in make these chapters a joy to read. There were plenty of subjects that were new to me and especially the chapters on human mosaics and chimaeras at times made my eyes widen in astonishment. I envy the reader for who all this material is new – you are going to have a lot of fun reading this book. In that sense She Has Her Mother's Laugh acts like a portal, introducing you to a huge number of topics relevant to heredity from which you can branch out to read more into areas of interest. The press has heaped praise on this book, calling it magisterial and sweeping. Having devoured the book from cover to cover in a day and a half, I can assure you this is no hyperbole. Zimmer has written an epic book that provides a vast panorama on our current and past understanding of human heredity and genetics.