She Has Her Mother’s Laugh

She Has Her Mother’s Laugh
Author: Carl Zimmer

Synopsis

This book, a truly sweeping and exhilarating excursion into the world of the gene, advances the view of heredity as a double-edged sword, ‘the inheritance of a gift, or a curse‘ (page 6). Providing a panoramic view of the subject, the author eloquently describes the profound influence of the science of genetics on human society, both by its positive applications in health, and by its disastrous  misuse in terms of social and racial segregation, slavery, and genocide (pages 19-20). The book also painted a detailed picture of the current state of the art, demonstrating how cutting-edge advances are explaining our ‘physical differences‘ and continuously redefining what it is to be human (pages 213 and 182-186). The author’s conversational writing style is complemented with the extensive personal references he makes, from sequencing his own genome, to seeking ‘heredity’s imprint‘ in his daughter Charlotte, who he discovered ‘has her mother’s laugh‘ (page 5). As it expounds the principles of genetics, the book also debunks the myths and misconceptions that have grown around the subject, for example when it dispels any biological basis for the concept of race with reference to Mitochondrial Eve, our common maternal mitochondrial ancestor, and with solid research findings by the likes of geneticists Theodosius Dobzhansky and his protege Richard Lewontin (pages 190-210).

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At the heart of the book is its thrilling account of the history of heredity in which the author charted the exhilarating landmarks that defined genetics as a scientific endeavour. In doing this, the book traced the birth of the field to the ingenious experiments of Gregor Mendel, the monk who deciphered the modes of genetic transmission, but whose work was tragically neglected until it was re-discovered by William Bateson, the man who gave the science of heredity the name ‘genetics’ (pages 39-40 and 60). Also featuring prominently is the work of Thomas Hunt Morgan on the fruit fly Drosophila melanogaster, brilliant research which established that genes are carried in chromosomes, and which showed that ‘many genes could influence a single trait‘ (pages 97-101). In similarly graphic accounts, the author charted the work of Theodor Boveri on sea urchins which demonstrated that chromosomal abnormalities can result in cancer, and the breakthrough discovery of the structure of DNA through the genius and intrigues of Rosalind Franklin, Maurice Wilkins, James Watson, and Francis Crick (pages 352-354123-125). Relatively more recent genetic developments which the book explored included the discovery of X chromosome inactivation by Mary Lyon, who worked against the ruthless antagonism of geneticist Hans Gruneberg; and the discovery of the bacterial CRISPR-Cas9 gene editing system, driven by the insights of Jennifer Doudna and Emmanuelle Charpentier (pages 335-342 and 491-497).

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No account of the history of genetics is complete without portraying its eugenic past, and this book does so with a thorough scrutiny of the key personalities and institutions who misused the emerging science of genetics to justify their shameful beliefs. Central to the book’s narrative in this regard is the Vineyard Training School in New Jersey, an establishment which ‘holds an important place in the history of heredity’ because it promoted the reproductive sterilisation of people it designated as ‘morons‘. The most infamous role in this sad saga was played by the psychologist Henry Goddard who believed that ‘feeblemindedness‘ was a heritable trait, and that ‘people who took up a life of crime or alcoholism might somehow taint future generations’. The author chronicled how, in his zeal to prevent the United States from ‘sliding into a crisis of heredity‘, Goddard collaborated with geneticist Charles Davenport, and fieldworker Elizabeth Kite, to fabricate a family tree for Emma Wolverton, a resident of the School; they used this bogus genealogy to falsely attribute a genetic basis for Walverton’s presumed feeblemindedness (pages 68-83). Even though his work was unscientific and unethical, a ‘natural experiment in heredity (that) never happened’, Goddard went on to publish a fictional account of Wolverton in The Kallikak Family, a book that played an influential role in normalising eugenic practices; it not only swayed the Supreme Court to forcibly sterilise another famous victim of eugenics, Carrie Buck, but it also guided the development of the Nazi eugenic policies that resulted in the killing of the mentally disabled and the physically deformed, eventually culminating in the much larger-scale Holocaust (pages 93-96 and 103).

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A compelling feature of the book is its fascinating account of the discovery of the genetic mutations that result in disease. In this regard, it depicts the history of phenylketonuria as a story that not only ’embodies the triumph of genetics’ but also demonstrates ‘the deep flaws in…gene-centred research’ (pages 132-133). The author described how  the biochemist, Asbjorn Folling, first established phenylketonuria as a genetic disorder when he studied Carol Buck, daughter of the Pulitzer and Nobel Prize winning writer Pearl Buck. The author depicted how the disease made Carol give off ‘a peculiar musty smell‘, and it explained that her urine was ‘loaded’ with phenylpyruvic acid because she was unable to break down phenylalanine (pages 106-116). Another striking historical anecdote concerned the Habsburg jaw, a genetic trait that has been inherited by generations of European royalty from the Roman Emperor Charles V; this striking trait manifested with a jutting jaw and a mouth that hangs open (page 11). Other historical references in the book included accounts of many discredited theories of heredity such as pangenesis by Charle’s Darwin, and inheritance of acquired characteristics by Jean-Baptiste Lamark (pages 167-174).

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Beyond the conventional topics of genetics, the book also provided enlightening perspectives of many lesser appreciated genetic phenomena. An intriguing theme in this context is that of chimerism or cellular mergers, a phenomenon that develops when twins acquire stem cells from each other whilst still in the uterus, and which explains why twins may possess two different blood groups (pages 377-380). A more dramatic manifestation of chimerism, illustrated with the famous cases of Lydia Fairchild and of Karen Keegan, is how it causes an otherwise irreconcilable mismatch between the DNA of a child and its mother, a situation that raises interesting legal questions about the biological maternity of the child (pages 382-385). Similarly fascinating is when the DNA of a foetus passively transfers to its mother through blood, a phenomena that makes the mother a genetic chimera (pages 385-386). Microchimerism is a related situation whereby foetal cells cross over and circulate in the blood of the mother even decades after the pregnancy; whilst this anomaly may boost the mother’s immunity, the author noted that it may also increase her risk of autoimmune disorders (pages 387-391). A similarly curious phenomenon the book examined is mosaicism, a condition whereby genetic mutations develop only in some cells of the body, and which may manifest as port wine stains, Blaschko’s lines, hemimegalencephaly, Proteus syndrome, and even cancer (page 350-359).

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The diversity of topics the book covered accurately reflects the extensive influence of genetics on individuals and populations. For example, in reviewing the impact of genetics on personal traits, the author pointed out that more than 800 genes influence variations in height, and their effect manifests with such interesting observations as how ‘Latvian women have become the tallest women in the world’ (pages 280 and 269). The genetics of intelligence was also a noteworthy subject, the book referring for example to the Flynn effect – the phenomenon that describes how population intelligence has been increasing with successive generations (pages 291-308). In discussing the significance of genetics to human health, the book referred to how the biologist Peter Medawar advanced the safety of organ transplantation when the translated the findings of research in freemartins – fraternal calf twins who do not reject each others cells because they have transplanted each other’s stem cells in their bone marrows (pages 372-376). Other exciting themes explored in the book were genetic manipulation, microRNAs, epigenetic inheritance, genetic and mitochondrial replacement therapies, genetic enhancement, paleogenetics and Neanderthal DNA (pages 30-33, 392, 430-442, 479, 507-522, 528-529 and 225-249).

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Opinion

This is a comprehensive, if slightly disjointed, account of a topic that plays an important social and healthcare role. It is a finely balanced mix of the journalistic with the academic, combining the past and future of genetics, and discussing its profound social and health implications. The book was particularly enlightening in its elucidation of complex concepts such as those of mosaicism and chimerism. Some parts of the book, such as the section on intelligence, were slightly overdrawn, and there were some errors, such as the assertion that Huntington’s disease does not affect people under the age of fifty. The gripping prose, the diversity of topics, and the interesting anecdotes however by far compensate for these minor flaws.

Overall assessment

This book is a most illuminative narrative of several genetic concepts which the author demonstrated with helpfully illustrative anecdotes. The book provides a very helpful view of the practical dimensions of these concepts especially as they relate to healthcare. Its in-depth account of emerging genetic investigations and therapies are particularly relevant as they are redefining the practice of medicine and influencing its future direction. The ideas in the book are critically important to several healthcare spheres and I recommend it to all doctors.

Book details

Publisher, Place, Year: Picador , London, 2018
Number of chapters: 19
Number of pages: 656
ISBN: 978-1509818532
Star rating: 4
Price: £15.99

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