In 1992 biological anthropologist Helen Fisher released the book “The Anatomy of Love: a Natural History of Mating, Marriage and Why We Stray.” It looked to human history, biology and animal behavior to explore the primordial urge to love and be loved. Nearly 25 years later, Fisher has come out with an update. This edition incorporates her pioneering brain research on lust, romance and attachment. It theorizes about how we choose who to love. And it looks at how the Internet has changed courtship and marriage. A conversation with Helen Fisher about “The Anatomy of Love,” a quarter century after it was first released.