X in Sex: How the X Chromosome Controls Our Lives

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X in Sex: How the X Chromosome Controls Our Lives by David Bainbridge
X in Sex: How the X Chromosome Controls Our Lives by David Bainbridge

“a woman is, as it were, a mutilated man, for it is through a certain incapacity that the female is female”image20

Aristotle: Generation of Animals
“Thus man … is the active principle while woman is the passive principle because she remains undeveloped in her unity”

Hegel: Philosophy of Nature
“Let the woman learn in silence with all subjection. But I suffer not a woman to teach, nor to usurp authority over the man, but to be in silence. For Adam was first formed, then Eve. And Adam was not deceived, but the woman being deceived was in the transgression.”

First epistle of Paul the Apostle to Timothy

WHAT is the spark of sexuality that triggers a child to become a boy or a girl? In this book, I hope to show you how this spark drives us to become men or women – people apparently so different, but made from the same stuff. Although many people are aware of the principles by which we are allocated our sex, I suspect that few realise that this is a story rich in history, evolution and philosophy which challenges our views of society.

We humans use an unusual method to decide our gender, and it can have dramatic effects on the way we live our lives. It may help many of us become ‘normal’ men and women, but it also consigns many to a life of disease, disrupts the everyday running of our body, and has even forced women to live a bizarrely double life. The actual physical entity that causes all this upheaval is a little nugget of life called the X chromosome, and this book tells its story.

A chapter by chapter synopsis


Why are some born girls, some boys, and some neither?

Male and female. He and she. Impregnator and gestator. The duality of the human race is such an inescapable part of our existence that throughout much of history few have even wondered why it is so. Just as every person is irrevocably allocated a sex at birth, so is sexuality itself woven through the whole of human life. Ever since the ancient Greeks, philosophers have pondered how it is we are allocated our sex. How can we inherit our sex from our parents – each of us has a male and a female parent, so what is the germ we inherit from them that pushes us one way or the other?

This chapter tells the story of how our sex chromosomes were discovered – fortuitously, as is usually the way with major scientific breakthoughs. We soon realised that our X and Y chromosomes were as different as is imaginable, and yet this has helped to explain how they have evolved from a single common ancestor chromosome millions of years ago. Even more remarkably, it now appears that X and Y are by no means the only way to decide an animals sex, and this chapter also takes us on a whistlestop tour of some of the more disreputable alleyways the animal kingdom’s sexuality.


Chromosome? Genes? DNA? What exactly are all these things? After all, I could hardly write a book about the inheritance of sexuality without trying to tell you. And in five snappy pages I will. Amaze your friends with your newfound knowledge!


Why do men get so many more genetic diseases?

Men are XY and women are XX. So what? Well, as I hope to explain in the rest of the book, this bland little sentence has immense implications for the biology of both sexes. In this chapter, we will see how men are at immense risk because they carry only one X chromosome. If that is damaged, they are consigned to a life of genetic disease. A random mutation in the X chromosome carried by the sperm destined to help create Queen Victoria caused a web of disease to spread throughout the royal families of Europe – resulting in death, disease and even the Russian revolution.

\Today, boys are still far more prone than girls to genetic disease because of this oversight. This chapter examines how diseases ranging in severity from colour blindness to muscular dystrophy are caused by damage to boys’ lone X, what can be done about them, and why they are not lost from the human population. Is it even possible that some of these diseases may confer some sort of advantage?

Interlude: HOW SEXY IS X?

It is called a “sex” chromosome, after all, but is there really anything inherently sexy about it. In fact, for reasons that are only gradually becoming clear, it now appears that both X and Y serve as repositories for genes related to reproduction. It has even been suggested that male homosexuality is ‘carried’ on the X.


Why is there a unique internal conflict inside women?

Perhaps the post remarkable result of the way we determine our sex is that women are a mixture of two different types of cell. One half of them uses the X chromosome they inherited from their father, the other half uses their mother’s. These cell types are arranged in little patches that can even be visible when one of them carried a genetic disease.

This bizarre double life that women lead had strange effects on their biology – it may explain why they split apart more often than boys to form ‘identical twins’; it may explain why female identical twins are never as similar as male identical twins; it may even explain why women’s bodies are more often torn apart in the civil war of autoimmune disease.


Our understanding of the genetic basis of our sexuality has led to an astounding breakthrough – just by selecting particular sperm based on their chromosomal content, we can now control the sex of our children. Is this safe? Is it legal? Is it ethical here? Is it ethical anywhere? Who really suffers when we do it? And who should decide?

Reviews and comments – feel free to send me more!

The book was awarded the 2004 American Medical Writers Association book prize.

There are many literary stars in the firmament of writers on evolution, and to a man they write with dash and persuasive logic. David Bainbridge is one such and in his latest book he takes the reader through the glories of the X chromosome at a cracking pace.

Miriam Stoppard, Times Higher Education Supplement

The X in Sex is absolutely fascinating, so intriguing, in fact, that I found myself unwilling to put it down. David Bainbridge surveys an astonishing amount of new information from recent genomic studies of the X chromosome, clearly explaining the findings in a way the average person can easily follow. The science is presented via amusing and highly appropriate metaphors and clever turns of phrase, all of which serve to brighten the prose and present the reader with catchy ways to think about complex ideas. This is an informative, authoritative, and thoroughly enjoyable read: one of the best books I have read in years.

Jane Lancaster, Scientific Editor of Human Nature

If you have ever been in intrigued by the puzzles of genetics – why boys tend to get haemophilia or colour blindness while girls are more likely to have an identical twin or to develop rheumatoid arthritis in later life – then The X in Sex is for you.

Chris Tyler-Smith, Times Literary Supplement

David Bainbridge takes us on a fascinating tour of X chromosomes and explains what the possession of these intricately folded, infinitesimally narrow, two-inch long strings of genetic codes weighing almost nothing, means for their bearers — that is for each one of us, male and female. History and personal anecdotes are woven together with up-to-date summaries of the science, punctuated with Bainbridge’s zany – and very British – humor, so that this information-packed book is pure pleasure to read.

Sarah Blaffer Hrdy, author of ‘Mother Nature: A History of Mothers, Infants and Natural Selection’

This is wonderful stuff – beautifully written, clear, jargon-free, with anecdotes sure to hold the attention.

Tim Birkhead, author of ‘Promiscuity: An Evolutionary History of Sperm Competition’

David Bainbridge … moves with ease between straightforward accounts of biology and historical stories about its effect, like the chapter describing the progression of hemophilia through the royal houses of Europe. Bainbridge discusses cultural history as well as natural history, and his wit enlivens every page (he talks about the “almost tantric self-control” of a hermaphrodite fish that resists self-fertilization). He also shows admirable restraint, punning on the word “inconceivable” just once.

Christine Kenneally, New York Times

The question is not so much why women and men are different (a worn topic that’s the subject of too many Mars-and-Venus bestsellers) but far more specific and far more interesting.

Liza Mundy, Washington Post

Just as sexual chromosomes come together in pairs, so do books about them. The X in Sex, by David Bainbridge, bills itself as as passionate defence of the X chromosome but veers into much of the same territory as [the author of the other book reviewed in the same article], often with more lucidity.

Joy Press, The Village Voice

The fascinating story at the heart of David Bainbridge’s charming and informative book manages to link calico cats, the original Eve and rheumatoid arthritis.

Jerome Burns, Financial Times Magazine

In his structure/function analysis of the X chromosome, Bainbridge provides a tongue-in-cheek, yet informative, description of one of the two human sex chromosomes.

R. Adler, Choice

His story weaves science, history and the history of science (with a little religion for good measure) in a straightforward, anecdotal fashion that will appeal to scientists and non-scientists alike. The science is clearly explained, and is illustrated with fascinating examples.

Mark T. Ross (Director of the X Chromosome Group at the Wellcome Trust Sanger Institute), NewScientist

Putting [the X chromosome] on a pedestal, as this writer does, allows her to be examined in humorous and insightful ways. Bainbridge’s humorous approach and beautiful expression of the facts has encouraged me to go to my favorite internet site and order his other books.

Florence Haseltine, Nature Medicine

The success of Bainbridge’s book stems from his clear and interesting descriptions of complex concepts and from his deft enhancement of well-known material with rich scientific nuggets. To the author’s credit, he delivers his messages with scientific acumen and good humor … Some of the questions that Bainbridge answers are rarely addressed sufficiently in other accounts.

Nancy Segal, Science

Although peppered with humor, Bainbridge never loses sight of the seriousness of this subject…throughout the book, Bainbridge skillfully relates biology to the history of the science, telling the entire story within the context of the interplay between science and society.

Kevin M. Kelly, American Journal of Human Biology

Accessible and intelligent science writing to not often go together, but Bainbridge succeeds.


Bainbridge has written a wonderful exposé of sex. His use of anecdotes, clever illustrations, and solid historical and scientific information is skilful.

Dolores Christie, Magill’s Literary Annual

The crucial factor, David Bainbridge argues in this lively and thoughtful new work, is the X chromosome and the fact that women have two of them, and men have an X and a Y. Drawing on a wealth of scientific material, but explaining it in an accessible fashion, Bainbridge illustrates how this fact determines a person’s sex and other physical features.

Beyond his illuminating scientific discussions, Bainbridge’s lively cultural history of how scientists have struggled with the question of sexual difference makes the X in Sex a compelling and entertaining read. Yet Bainbridge never loses sight of the seriousness of his topic and offers a thoughtful perspective on how biology and culture shape who we are.

Seminary Co-op Bookstore Reviews

He has sufficient knowledge, as well as the extraordinary ability to communicate it in a breezy, highly readable fashion that is both entertaining and informative.

Barbara Migeon, American Journal of Human Genetics

This is popular science in fine form — both entertaining and informative.

Bainbridge morphs with ease from biologist to historian, drawing on a wealth of material to highlight major genetic discoveries, while painting a rich philosophical and historical picture that brings into consideration not only the biological but the religious, cultural, and ethical implications of each advance.

Bainbridge provides a prime example of science made amusing and accessible — a rare combination. His dry and lively wit suggests that some anecdotes and turns of phrase were written with a wink and a smile, and this slim volume should appeal to scientists and nonscientists alike.

Overall, The X in Sex represents a jargon-free journey for the layperson interested in (some of) the reasons why men and women are so different..

Brooke Urquhart Grindlinger, Journal of Clinical investigation

Bainbridge writes a thoughtful exploration of a very pertinent topic in a time where technology is increasingly opening up the possibilities for genetic manipulation to create children with certain characteristics.

Yunie Kim, Yale Journal of Biology and Medicine

A fascinating, often humorous analysis of the science of sexuality.

Gilbert Taylor, Booklist

An excellent example of good science writing that will also appeal to general readers.

Library Journal

Lively, witty … a fine demonstration of science made accessible.

Kirkus Reviews

1 thought on “X in Sex: How the X Chromosome Controls Our Lives”

  1. David Bainbridge’s Sex: How the X Chromosome Controls Our Lives is an absolutely fascinating read. This book takes a detailed look at how the X chromosome influences our lives, and it does so in a clear, compelling way. The author examines both the biological implications of having an X chromosome and its social implications, providing readers with an incredibly comprehensive understanding of what it means to be a woman or man.

    The book contains many interesting facts about the role of the X chromosome in sex determination, as well as in other areas such as intelligence, hormones, personality traits, and even physical characteristics. Mr. Bainbridge has also included numerous case studies from his own research which demonstrate fascinating correlations between genetic make-up and behavior. He also provides helpful explanations of current theories on gender differences that can help us better understand why there are differences between men and women.

    Overall, this book is an excellent resource for anyone interested in learning more about the X chromosome and its role in shaping our lives. It is written in an engaging style that will appeal to both laypeople and experts alike. Highly recommended!


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