Brain Sex is a popular market book about the biology of gender, the biological differences between men and women, by Anne Moir (geneticist) and David Jessel (journalist), first published by Michael Joseph (a division of Penguin) in 1989. The sequence of chapters broadly follows the human life cycle — birth, maturity, reproduction.
The first chapter of the book establishes the state of the gender debate at the time of publication. It acknowledges that the majority opinion of educated people (at the time of publication) was that men and women have the same brain. However, it claims that this is in stark contrast to the opinion of research scientists in the area. There is a cursory literature review of a century of sex research, featuring some early crude and unreliable results (the book's assessment), but proceeding to the modern results available from about the middle of the 20th century.
In chapter two, the authors begin their systematic presentation of the scientific data. It starts by explaining sexual reproduction, the sex determination system and X and Y chromosomes. It extends beyond this to late 20th century discoveries regarding the effects of hormones on brain formation in