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Between XX and XY: Intersexuality and the Myth of Two Sexes [Hardcover]

Gerald N. Callahan PhD

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Book Description

July 1 2009

“On October 10, 1970, the day she was born, she was named Dorothy Maree Alaniz--a baby girl. Curiously, though, no one filled out a birth certificate that day. When the certificate was finally filed on November 5, the name on it was Rudolph Andrew Alaniz. Within less than one month after her birth, this girl became a boy.”


Every year in the United States, more than two thousand children are born with an intersex condition or disorder of sex development. What makes someone a boy or a girl? Is it external genitalia, chromosomes, DNA, environment, or some combination of these factors? Not even doctors or scientists are entirely clear. What is clear is that sex is not an either-or proposition: not girl/boy, XX/XY, switching between two poles like an on-off switch on a radio. Rather, sex is like the bass and treble knobs on that radio.


Between XX and XY provides a fascinating look at the science of sex and what makes people male or female. There are people born XXY, XXXY, or XXXXY, or with any number of variations in X or Y chromosomes, but those who do not fit into society’s preconceived notions about sex often face a difficult path in life.


Dr. Callahan explores why humans are so attached to the idea of two sexes, and examines our obsession with sex and sexual intercourse through the ages.

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"Callahan does a good job of exploring intersex individuals, who are neither male nor female, and argues that they need to be accepted for what they are and not viewed as defective."  —Publishers Weekly

"Immunologist Callahan takes a fascinating look at the biology and human experience of intersexuality, a state in between male and female."  —Discover Magazine

"Callahan's writing style is both accessible and engaging; it reads more like creative non-fiction, a la Malcolm Gladwell."  —Ms. Magazine

"This is a fascinating, easily understandable journey into why we are born male or female and examines our age-old obsession with sex."  —Fort Collins Coloradoan

"There are lots of interesting nuggets here—for example, Callahan's description of biological sex as a spectrum, not a binary system."  —Double X

"The book is really beautifully written, highly accessible, and visionary in its own right."  —Feministing

"This book takes readers through an alphabet of gender and gender variations. Callahan shows readers that rather than either/or scenarios, there have always been variations; his book shatters our society's take on pink and blue."  —

About the Author

Gerald N. Callahan, PH.D., is an author and an immunologist/pathologist with more than thirty years of experience in biomedical research. He is the author of Infection: The Uninvited Universe and Faith, Madness, and Spontaneous Combustion: What Immunology Can Teach Us About Self-Perception. He is currently an associate professor at Colorado State University.

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Most Helpful Customer Reviews on (beta) 2.7 out of 5 stars  7 reviews
19 of 21 people found the following review helpful
3.0 out of 5 stars Good primer on the complexities of biological sex July 19 2009
By Audacia Ray - Published on
If you've never thought beyond the concept of "opposite sexes" this is a really great primer. If you're a gender and sexuality nerd like me, you won't learn a whole lot of brand new stuff from this book.

Callahan spends a lot of time debunking the myth of the two sexes - there's slightly more in the book about that than there is about disorders of sexual development or intersex. If you're looking for a really in-depth read that focuses on intersex, this isn't that book. But if you're looking for some more general stuff about the science of the differences between men and women and genetic variations that will tweak your concepts of "men" and "women", this book is very much worth your time.

Callahan was able to write a very readable book that didn't bore me or confuse me at all, even when he writes about chromosomes and karyotypes and stuff. In addition to good content about human sexuality, he devotes a good amount of time to writing about hermaphroditic animals, which is fascinating stuff and will further erode your notions of a two-sex model. The case studies of intersex people included in the book are also engaging, though also pretty heartbreaking.

If you are up for something heavier, more theory-laden and more advanced about the differences among the sexes (see what I did there? implying that there are more than two sexes with grammar?), check out Anne Fausto-Sterling's Myths of Gender: Biological Theories About Women and Men. That book was originally published in 1987, updated in 1992 - so some of the science is a little our of date, but it's a really great and challenging read.
6 of 6 people found the following review helpful
4.0 out of 5 stars Good for beginners March 16 2010
By margadief - Published on
Format:Hardcover|Verified Purchase
I chose this book because of its synopsis and the reviews of others, and am glad that I did. The author's style is very readable and he makes a very complex subject understandable. While its obvious that he has definite opinions on this subject, he does a good job of keeping them in check while he writes. Presenting the history of our understanding of sex along with the current state of knowledge brings an historical continuity to the book, which was helpful. Excellent footnoting and bibliography for those who wish to read further. All the different intersex variations become a bit difficult to keep separate after awhile, but I suspect that's more my unfamiliarity with the subject than his writing.

This is a good book if you want a primer on the subject of intersexuality, either for yourself or as a gift.
4 of 4 people found the following review helpful
4.0 out of 5 stars Excellent overview Jan. 31 2010
By chinakids - Published on
Format:Kindle Edition|Verified Purchase
I suggest you have read some evo-devo before delving into this book. The premise is that gender is at least as malleable as eye color, body height and weight, and many other characteristics. Beyond that, there are many variations past XX and XY, and the current thinking is to place every child squarely into the XX/XY dichotomy. Additionally, recent medical practice has been to do so with or without consent of parents??? (no verification or sources of this) - a plea for acceptance of those that fall somewhere between these two endpoints - and an attempt at scientific explanation of how much diversity there is in between.

I recommend this book, even though I thought it could have been better written. The information is substantial and crucial to our understanding of gender.
3 of 5 people found the following review helpful
4.0 out of 5 stars hermaphrodite finds missing pages! July 5 2011
By J. P. Barber - Published on
Format:Kindle Edition|Verified Purchase
I am a hermaphrodite with Klinefelter syndrome and androgen insensitvity syndrome and I need to read every page of this book over and over, but I got to page one hundred and it went to page sixty-nine. Then the book goes to sixty-nine to one hundred and starts again on page 133. My medical records made by the U.S. Army found me to be a female hermaphrodite and I am trying to understand why I am now a female army officer. I will do what I can to help fix the problem and enrich the study of hermaphroditism which has three cases in my family. Jo XXY
0 of 2 people found the following review helpful
2.0 out of 5 stars Just OK Jan. 25 2013
By L M V - Published on
Format:Kindle Edition|Verified Purchase
This book is interesting and does a good job opening your mind to the idea that there is more to human sexual development than just male and female. It does however get deep into chromosome talk, karatypes, etc. Page after page of clinical words and detailed descriptions of different chromosomal variations. It read like a college textbook. That being said, there were also many real life stories about different intersexed individuals; some of which were interesting and heartfelt others of which were long winded and made me feel like I was reading a bad Harlequin novel. Overall I wouldn't recommend. There are better choices.

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