The nature-nurture controversy has never been more hotly debated. Scientists send shock waves through society whenever their new theories of what is biologically inherited - as opposed to socially learned - confront our old ideas about the self. The author, molecular geneticist Dean Hamer, is one of a group of researchers mapping the human personality. His findings help to explain why one brother becomes a Wall Street trader while his sibling remains content as a librarian.;Molecular biology shows that genes are the most important factor in distinguishing one person from another. Humans come in large part ready-made from the factory, yet genes are not fixed instructions. As the authors point out, it is our very nature to respond to nurture. This text is an investigation of the crucial link between our DNA and our behaviour.