This book traces the origins of courtship, marriage, adultery, divorce and remarriage back 4,000,000 years to the grasslands of Africa, examining those traits and tendencies of love that we inherit from our past. The author examines flirting and courting, explains love at first sight and why we fall in love with one person rather than another. She explores the brain chemistry of attraction and attachment and, looking at divorce and adultery in societies around the world, proposes a new theory of the four-year itch, which explains when and why most marriages are most likely to end.