The cleft / Doris Lessing.

Enhanced descriptions from Syndetics:

From Doris Lessing, "one of the most important writers of the past hundred years" (Times of London), comes a brilliant, darkly provocative alternative history of humankind's beginnings.

In this fascinating and beguiling novel, Lessing confronts the themes that inspired much of her early writing: how men and women manage to live side by side in the world and how the troublesome particulars of gender affect every aspect of our existence.

In the last years of his life, a Roman senator retells the history of human creation and reveals the little-known story of the Clefts, an ancient community of women living in an Edenic coastal wilderness. The Clefts have neither need nor knowledge of men; childbirth is controlled through the cycles of the moon, and they bear only female children. But with the unheralded birth of a strange new child--a boy--the harmony of their community is suddenly thrown into jeopardy.