For those who continue to insist there are only two genders and one acceptable sexual orientation, this first book by retired Vancouver neuropsychologist Olive Skene Johnson compiles decades of scientific findings to the contrary. Study after study evincing the biological bases of hetero-, homo-, trans-, and intersexualities are catalogued herein, so voluminously as to become almost mind-blurring.

Although initially motivated to write the book by the discovery that her two eldest sons were gay, Johnson leaves little room for personal touches or rhetorical devices in this data-driven narrative. The prose is clear and strictly functional, well-suited to simplifying for a lay audience the specialist dialects of scientific research.

Although the book is somewhat dry at times, this lack of embellishment is one of its greatest strengths. In a field of discourse too often monopolized by rampaging prejudice masquerading as argument, Johnson’s straightforwardness comes as welcome refreshment.

The book is logically structured, moving from the biological differences between males and females to those between various sexual orientations, all the while emphasizing the limitless varieties within each category. The thoroughness with which Johnson documents how prenatal hormone levels set lifelong parameters on the developing brain places her firmly against those who still label sexual orientation a “preference.” But she is moderate in her assertions, allowing the evidence to do the arguing, and fully acknowledges the interconnectedness of biological and social factors in their bearing on human life. Biology sets parameters, while society helps determine which possibilities become manifest.

So although her liberal-mindedness is clear from the outset, Johnson’s approach precludes any criticism of her integrity. Above all, The Sexual Spectrum is a sensible book. No one who reads it will be able to view discrimination on the basis of sexuality as anything other than the irrational bigotry it is. And moreover, many readers will come away with a heightened appreciation (and respect) for the kaleidoscopic variety of our species.