This book offers a tantalizing answer to an age-old question: Why did big-brained Homo sapiens suddenly emerge some 150,000 years ago? Drawing on an awesome breadth of research, Shlain shows how, long ago, the narrowness of the newly bipedal human female’s pelvis and the increasing size of infants’ heads precipitated a crisis for the species. Natural selection allowed for the adaptation of the human female to this environmental stress by reconfiguring her hormonal cycles, entraining them with the periodicity of the moon. The results, however, did much more than ensure our existence; they imbued women with the concept of time, and gave them control over sex—a power that males sought to reclaim. And the possibility of achieving immortality through heirs drove men to construct patriarchal cultures that went on to dominate so much of human history.

From the nature of courtship to the evolution of language, this brilliant and wide-ranging exploration stimulates new thinking about very old matters.