This is a good overview of what science currently has to say about the biological underpinnings of sexual orientation. The author himself is gay, which lends more credence to his apparently even-handed review of the evidence for various theories behind the development of sexual orientation. Although there is not single line of evidence that unequivocally explains the biological roots of secual orientation, it is quite clear that sexual orientation is primarily biologically determined to a great extent, but that the complexity involved is great enough that there may be more than on way that sexual orientation gets determined. LeVay does conclude that the primary factor is probably the quantities and timing of testosterone levels during fetal development that are the primary factors, with the potential varying response of the fetus to the presence of testosterone.

The one gripe I did have with this book is that although a few intersex conditions such as adrenal hyperplasia and CAIS are brought up to provide evidence for the underlying role of hormones during development, LeVay never uses the term intersex in reference to these conditions. I do not know whether this is because he thinks using the term intersex might add complications, or that he somehow does not consider intersex to be a valid condition. It seems like in a book of this nature, a clear mention of intersex is needed, which left me disappointed. ( )

Fascinating, super educational, and very easy to read for such a science-y book! ( )

This is a necessary book, which comes at an important time.

Back in 1991, LeVay made one of the key scientific breakthroughs in understanding the dynamics of sexal orientation. Since then, he's devoted much time and energy to informing the public discourse around matters of sexuality.

This book aims to play a role in that discourse—to make sure we recognise the limits of our knowledge, and the limits of science itself. And to make sure that what we do know for sure, is interpreted properly.

He writes with both detail and clarity. He makes the science accessible to the lay reader, but doesn't dumb it down.

LeVay doesn't shy away from a key fact which may be uncomfortable to some; that, on average, aspects of the gay brain and gay behaviour tend to conform to the opposite gender. There is some basis, it seems, in stereotypes.

But stereotypes only go so far. Lurking in the book is a cruial, and much more interesting observation. While sexual orientation—especially male sexual orientation—tends to be fixed, behaviour and personality are not. There's a wide variation in the statistics LeVay quotes. Gay men are as different from each other, as they are from their straight counterparts.

And whether the mechanism is genetic, congentital, neo-natal or psychodynamic, no single theory can explain why a particular man or woman becomes gay.

LeVay emphasises the importance of this fact. It would seem that there are many ways to become gay, and they produce a wide array of gay sexualities. This science reflects the subjective experience of most gay men and women.

But, alas, in its fetish for finding a single "cause" for homosexuality, science has not addressed this point. In fact, science has only begun to scratch the surface.

When covering the science, LeVay repeatedly has to qualify his remarks; many of the studies he cites have not been replicated, or confirmed, or followed up. Even his own ground-breaking work was a small study; published, it seems, as a by product of other investigations. The science of same-sex attraction, LeVay reminds us, has a long way to go. ( )