Identically Different

By Tim Spector
The Orion Publishing Group, 2012
293 pages (sb)
ISBN 9780297866312

Reviewed by Deborah Gale

We seem to possess a natural curiosity when it comes to twins.  Identical twins are hard to ignore but even fraternal twins can look and talk alike. Throw in some similar facial expressions or mannerisms, attributes we as humans seem to pick up on, and twinning holds endless fascination. This is particularly true for researchers and for me. I happen to be the mother of two sets of naturally occurring twin daughters. Our identical twins followed their fraternal sisters and were born four years apart.  Interesting at the time, they even shared the same predicted due date but ended up being born five days apart. Consequently, this book, packed with case studies, anecdotal evidence, biomedical explanations and statistical support held more than passing interest for me. Tim Spector, is the Professor of Genetic Epidemiology at King’s College, London. He is also responsible for the existence and directorship of the largest Twins register in the world. In this book he offers an entertaining and broad sweep of our rapidly changing understanding of the genetic material that makes us tick.

Compelling historical perspective readies the stage for an exhaustive exploration of popular culture’s interpretations and misconceptions of recent genetic research. Surprisingly, the first proper twin studies were conducted only 80 years ago. While controversial and often criticized, these now form the backbone of our knowledge and perceptions of disease, behavior and how both are subject to major genetic influences. That said, using genetics to treat diseases and understand behavior is far more complicated and difficult than was originally expected. Not since the 1950’s, when the double helix of DNA was first discovered, has the quest for a solution to the genetic riddle seemed more convoluted.

Epigenetics

Professor Spector challenges long held assumptions about genetic destiny in this exposé on the burgeoning field of epigenetics, or the soft inheritance capabilities of our genes.  He opens with the assertion that the traditional debate between nature and nurture lost its relevance a dozen years ago, when it was supplanted by the first sequencing of the human genome. Epigenetics is basically the study of what happens when methylation occurs. This is the switching on and off of genes that starts or stops them from working or “being expressed”. Gene expression is a natural process and it can be passed on across generations. It is notable that while Darwin’s natural selection theory predated our knowledge of genes, his work on evolution actually included a role for acquired inheritance. Spector’s spotlight on epigenetics provides readers with regular examples of how it is possible for the effects of our grand parents dietary habits and behaviors to be passed on for several generations before fading. He demonstrates that this is a reversible while inherited change that does not alter the basic structure of the inherited DNA.  For example, we now know that even though identical twins share the same structural DNA, different chemical and electrical signals get produced at the cellular level. These can alter the DNA and produce different behaviors in identical twins. This in turn helps to explain human adaptability to new environments.

Spector takes readers through a review of the gene hype we read about in the news every day. He looks at the popularization of certain heritable characteristics to challenge conventional myths and devotes a chapter to each one. He explores prototypes linked to happiness, belief in God, natural talent, effectiveness of parenting, criminality, obesity, sexuality, longevity and even fidelity to demonstrate the extraordinary neuro–plasticity, ie adaptive malleability, of the human brain. In every instance, studies provide evidence that life stresses are likely to influence us because of their epigenetic effects on our genes. This confirms that while gene influences are important, they are no longer the dominant factor. Genes are linked to mindsets however, including those that shape spirituality. These, as well as personality traits, are capable of modification and resetting.  In all of Spector’s substantial twin’s research he has been most surprised by his investigations into the three dimensions of religiosity: belonging (affiliation), behaving (attendance) and believing. Human beings appear to share a variable while innate inherited sense of the spiritual and this affects the way we perceive the temporal world, our corporal selves and the limits of the universe. Epigenetics research posits that genes for faith susceptibility, the soft inheritance from our ancestors, can’t disappear.

Body hair removal

Throughout his book, Spector employs interesting examples to advance his epigenetic argument while simultaneously deflecting our attention away from the imprecise and random nature of heritability. Using one very topical development, he links susceptibility to religion with the current trend for complete body hair removal by western females under 40. While full depilation for females has been normal for specific religious groups in particular geographies for centuries, Spector explains how this trend went mainstream in the west and only since 2000. He borrows the concept of ‘memes’ or the cultural equivalent of genes, from the controversial author Richard Dawkins to advance this argument. He pinpoints the combination of easy internet access and the reduction of opportunities for female communal bathing to the rapid transmission of a “no–body–hair” cultural message. In turn, more women came to believe this practice to be more common than it actually is and provides rich pickings for the feminist readership.

The London Cabbie

In another case, he used the cabbies in London to explore IQ and talent. For black cab drivers, mastery of “The Knowledge” is demanded for success in their livelihood.  Brain scans were taken of cabbies when they were still driving and again after they retired. These showed that the drivers had a larger hippocampus, the part of the brain that controls memory and spatial imaging, than the retirees. It seems cabbies brains become reversibly larger while they are working, and not because of their genes or IQ. Rather, it was because of all the additional hours of practice they were putting in.  This and other studies, based on over 30,000 individuals, confirmed that while average heritability of IQ stands around 60%, the existence of natural talent might be overrated. Expertise seems to be more closely correlated to sufficient practice as well as the ability to focus on areas of personal weakness. That, and particularly those genes responsible for motivation, suggests once again that a particular mix of genes and environment are required for any measure of success.

“Junk DNA”

In the final two chapters, he considers the radical new thinking regarding microbial genomes or metagenomes. This is the gene sequence of the trillions of bacteria and non–human genes, particularly those lining our guts, now revolutionizing the way scientists believe diseases get passed down through generations. Even though we understand how DNA is replicated, how hereditary information gets coded and even managed to shrink the total number of genes to less than 23,000 what was until recently referred to as non–genetic or “junk DNA” has now been discovered to be anything but. In early September 2012, a global consortium of scientists published thirty research papers, simultaneously, in which important functions have been newly assigned to that junk.

Spector’s book provides a roadmap detailing how our genetic cognition has developed and shows us how quickly and how broadly we are trying to use this new information. There is research now supporting the identification of genes that determine facial morphology. In time these could have applications in forensic criminal investigations. Predicting eye and hair color via DNA is also a distinct possibility. Will coloured contact lenses and hair dye go the way of the Walkman?  Cosmetic manufacturers like L’Oreal, Olay and Estee Lauder are all focused on epigenetic research to understand how the environment influences cells in our modern quest to hold back the years.  That we can now infer age from a blood sample is further indicative of the scale of ongoing research.

It was only ten years ago that clinical psychologist Oliver James fired up the nurture debate when he reliably informed us to blame our parents because “They F*** You Up”. In 2012, Tim Spector has upped the ante to implicate our grandparents and beyond. With population ageing now recognized as undeniable and poised as the growth industry of the 21st C, explanations of why and how we can change our genes is timely. Gene technology can screen for rare diseases, target expensive cancer drugs to the most receptive patients and predict safe dosages. The clearest example of this is found in another recent announcement that breast cancer has been stratified into four major genetic categories. Translating these findings into targeted treatments is the future challenge.

Concluding thoughts

Surrounded by twins as I am, I was bound to like this book. Nevertheless, if ageing well is of interest, you will like it too. The factual information is well supported, though some of the celebrity inspired examples (like using Tiger Woods recent history to open the chapter on the fidelity gene) lower the tone of this otherwise excellent read.

Spector concludes by reminding us that genes are not destiny and that what we do to our bodies and what our grandparents did to theirs, does matter. Still, as AA Gill recently reminded us, we can’t stop the clock and while hubris and vanity still lead to the grave, we ought to try to get there on our own two feet.

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