The nature-nurture controversy has never been more hotly debated. Scientists send shock waves through the culture whenever their new theories of what is biologically inherited - as opposed to socially learned - confront our old ideas about the self.

Nowhere are these ideas more arduously tested than in the labs of molecular geneticist Dean Hamer, whose discoveries of specific genes linked to behavioral traits - such as anxiety, thrill-seeking, and homosexuality - prove without a doubt that we are in large part hardwired to behave the way we do. Hamer is one of a small group of researchers mapping the human personality.

Hamer shows how much of our behavior is heavily influenced by genes, including how much we eat and how much we weigh, how we think, how much we drink, use drugs, and have sex. He also sheds light on some of the most compelling and vexing aspects of personality, such as shyness, aggression, depression, and intelligence. Each chapter draws on the most cutting-edge research available and provides the reader with a blueprint for understanding himself and his family.

Then Hamer closes the book with a chilling scenario that imagines the inner life of a genetically cloned scientist's son.