Title: She Has Her Mother’s Laugh – The Powers, Perversions and Potential of Heredity
Author: Carl Zimmer
Publisher: Picador, 2018 (First)
ISBN: 9781509818549
Pages: 656
Heredity is a powerful tool with which life sustains and propagates itself on earth. Even though its effects were clear to every society, the methods by which it is transferred across generations came to light only in the twentieth century. With the discovery of genes and unwinding the mysteries of DNA, mankind basked in the tremendous potential the knowledge offered to enhance the wellbeing of people – and, by corollary, causing unforeseen consequences if the technology was not responsibly handled. Genes are the blessing and the curse that our ancestors bestowed on us. However, science identified many other factors that are equally crucial to the development of humans as genes. This book covers all these channels in excellent detail and provides a comprehensive view of genetic research. The single most important idea it gives off is that inheritance is a broad concept which propagates through DNA (what is usually called nature), environment (nurture), epigenetic (transfer of some acquired traits) and by teaching the young (culture). Even though these are quite diverse, a little consideration would show that the benefits it conveys to a living being are broadly of the same nature. Carl Zimmer is an American popular science writer, blogger, columnist, and journalist who specializes in the topics of evolution, parasites and heredity. He has authored many books.
The book provides a good overview of the study of heredity beginning from Charles V, the Habsburg emperor, to plant and animal breeding in subsequent centuries. Generations of interbreeding in the royal line resulted in specific genetic features such as a deformed jaw (later called the Habsburg Jaw) among the princes. Their overall health was very fragile too. Things got moving when Darwin appeared on the scene. ‘Origin of Species’ was one of the most influential books ever written. Darwin could not explain the biology behind why individuals varied and how traits are copied to the next generation. He believed that a trait acquired in life could be passed down to future generations. We read about Gregor Mendel and the birth of the concept of genes. Hugo de Vries discovered in the year Darwin died that every cell contained invisible particles that are responsible for passing traits from one generation to the next. He called them pangenes which was later shortened to genes.
When it was established that traits could be transferred to another generation, racism suggested the possibility that the white race was at the pinnacle of human evolution. Even among the whites, the Nordic stock was deemed to be superior. Whites suffering from genetic diseases ranked further lower in the hierarchy with blacks and coloured people going down to the bottom rung. A new branch of study called eugenics thought of ways to cleanse and thereby better the human stock. By the dawn of the twentieth century in the US, eugenicists wanted to improve the human stock by selective breeding and preventing people with genetic disabilities from having children. Across the ocean in Germany, it was copied by Nazis into a devilish strategy. It first targeted people with disorders (usually poor intellectual capacity) to be sterilized. Hitler established a set of racial hygiene laws. In the first year after establishing hereditary health courts, Germany sterilized 64,000 people and by 1944, the tally went up to 400,000 including the mentally ill, the deaf, gypsies and Jews. In 1939, Nazis started killing off people with hereditary disabilities. It is estimated that they eliminated 200,000 lives. In the US, the craze for eugenics sailed in the inverse ratio as its progress in Germany. American objectors of eugenics repudiated it as bad science and bad policy. The Eugenics Record Office was shut down in 1939. Eugenics is down for the moment, but it may spring back to life if a powerful backer comes to its rescue. How many of you did think of Donald Trump while reading these lines?
Zimmer gets into the question of whether a characteristic is heritable in the true sense of the term, that is, whether an organism will definitely suffer the consequences if a specific gene is present or missing in its genome. The gist of the discussion is that the linkage is too complicated to decide beyond doubt. Colour of eyes is a heritable trait. Citing the example of a genetic disease called PKU, the author argues that it showed a way to attack the idea that our intelligence is fixed by the genes. This is an unfortunate example for the argument however. The brains of these people get stunted and they end up with very low intelligence like a toddler. This is because the gene prevents the dissociation of the amino acid phenylalanine obtained from food which eventually reaches the brain and damages the nerve cells. If no treatment is made, it will lead to devastating intellectual disability. But if the infant is given a diet low in that chemical, the symptoms disappear. What this example proves is that genes are extremely important but in some cases, some alleviating measures can be found. This does not support the author’s logic that genes are not that critical. Then he takes up the case of height as a heritable trait. Here, the dependence on genes is as high as 86 per cent, but it is strongly linked to nutrition also. After each generation, the world is getting taller, not just in the developed countries. South Korean women grew eight inches taller in average height in a century, while Iranian men got taller by six and a half inches. The book then concludes that intelligence depends on several physical factors and genes that no direct relationship can be drawn. Studies held in Scotland suggest that lower intelligence test scores raised people’s risk of death. It’s possible that people who score higher may be better able to understand information their doctors give them. Genes still account for only a small percentage of the variation in people’s test scores. As with height, it has not been able to definitely prove which genes cause the effect to occur.
Race or racial purity is a concept which is associated with the genome of people constituting a society. Zimmer makes an extraordinary effort to conclude that race is not supported by DNA. He observes that the concept of race is not a feature of the natural world beyond our social experience. But this looks uncannily similar to the wokeish canard that gender is a social construct rather than biological. Hence, take it with a pinch of salt! Up until the middle ages, writers never used the word in the present meaning. Racial laws were common in the US as recently as half a century ago. The Racial Integrity Act passed in 1924 barred interracial marriages. It defined the white people as those whose blood is entirely white (of course, not in colour) having no known, demonstrable or ascertainable admixture of the blood of another race. This law would stand till 1967 when a couple’s wedding was annulled on its basis. They appealed to the Supreme Court which struck down the law. The author argues that if races were biologically significant, most of the genetic diversity should exist between races rather than between individuals of the same race. In the 1950s, Richard Lewontin made a study of a wide range of human populations which found that genetic differences between races was only 6.3 per cent, whereas the diversity within populations was 85.4 per cent. Even with this data, it somehow feels that something important and which can tip the scales has not been told. Since the subject is contentious, it is understandable that authors would prefer to bet on the side of the politically correct option. There is a brief analysis on contagious cancer, which was a scientific secret hiding in plain sight for two centuries. Eight cases were identified so far and they would not be the last. In the case of humans, the documented cases show a single leap (from one person to another and not more). It may be that our immune systems are so strong that cancers never get the chance to evolve into parasites that can leap from host to host.
The birth of a living being is something which is looked at with awe and wonder even by committed rationalists. This book furnishes a good discussion on how cell division takes place when a foetus is developed, clearly articulating the intricacies of the process and the pure amazement at one cell replicating to hundreds of types of totally different cells in different parts of the body. There is a startling narrative on human chimeras where the genome and proteins contain traces of another person, usually a twin, whose genetic particles get mixed up in utero. If two embryos of the same sex are involved, it’s much easier for them to go unnoticed. In the other cases, the blood of the person may carry cells of a different blood type. A case is listed where a person possessed male and female sexual organs. In the case of animals, an example is described where it carried the genetic imprint of two fathers. Obviously, this possibility is not examined for human cases. We also read about unusual instances of a mother’s DNA not matching her children. This happens when the mother was a tetragametic chimera (where one embryo develops into a person combining that of a should-have-been-twin). It is now known that foetuses can pass cells to mothers and vice versa, whose effects can last for several years after birth. Women who had given birth to boys carried cells with Y chromosomes. This book pushes the envelope of genetic research to the end of the 2010s. It looks like a whiff of Lamarckism is returning to science under the lofty title of ‘transgenerational epigenetic inheritance’.
The author unveils a chapter in the life of the famous writer Pearl S. Buck who is the author of the masterpiece The Good Earth. It was one of the four books with which I started my reading career. In fact, I’m not sure how many times I have read this superb novel. It was news to me that Buck started writing fiction just to save enough money to settle her mentally stunted daughter in a good institution. The child was suffering from PKU. There is a good discussion on gene therapies on somatic and germ lines such as CRISPR and mitochondrial, fully exposing the ethical and scientific concerns associated with them. The apprehension that this may lead to a new kind of eugenics is also very strong. In vitro gametogenesis offers the dizzying possibility of transforming on ordinary skin cell into a sperm or egg from which a baby can take shape. The author displays an unnecessary wokeish bias in the last chapter in accusing the whites of inheriting wealth way more than the blacks and suggests that this may be legally stopped. In a second case, he suggests that instead of using for disease eradication, CRISPR should be employed for saving endangered species, but he does not consider who would fund such research. This is also a wrong appreciation of the priorities.
The book is highly recommended.
Rating: 4 Star
