In America, we are demanding everything from our marriage.

Women have a better sense of smell than men do, and it's even sharper in the middle of their menstrual cycle, when estrogen levels peak and women are more likely to be deciding whether a man's attractive.

Romantic love allows you to focus mating energy. Attachment sustains that relationship as long as necessary to raise your baby.

In general, men are wired to notice obvious signs that convey interest in mating - a warm smile, for example - and ignore other subtleties, like if your lipstick is faded.

Romantic love is an obsession. It possesses you. You lose your sense of self. You can’t stop thinking about another human being.

Today, most women are surrounded by ingenious gadgets. They don't grow the peas or raise the chicken that they serve for dinner; instead they hunt and gather in the grocery store. They go through catalogs or department stores to buy clothes instead of shearing sheep, carding wool, and weaving cloth for skirts and coats and blankets.

You fall in love with somebody who fits within what I call your 'love map,' an unconscious list of traits that you build in childhood as you grow up. And I also think that you gravitate to certain people, actually, with somewhat complementary brain systems.