Book excerpt: Does biology help explain why women, on average, earn less money than men? Is there any evolutionary basis for the scarcity of female CEOs in Fortune 500 companies? According to Kingsley Browne, the answer may be yes. Biology at Work brings an evolutionary perspective to bear on issues of women in the workplace: the "glass ceiling," the "gender gap" in pay, sexual harassment, and occupational segregation. While acknowledging the role of discrimination and sexist socialization, Browne suggests that until we factor real biological differences between men and women into the equation, the explanation remains incomplete. Browne looks at behavioral differences between men and women as products of different evolutionary pressures facing them throughout human history. Womens biological investment in their offspring has led them to be on average more nurturing and risk averse, and to value relationships over competition. Men have been biologically rewarded, over human history, for displays of strength and skill, risk taking, and status acquisition. These behavioral differences have numerous workplace consequences. Not surprisingly, sex differences in the drive for status lead to sex differences in the achievement of status. Browne argues that decision makers should recognize that policies based on the assumption of a single androgynous human nature are unlikely to be successful. Simply removing barriers to inequality will not achieve equality, as women and men typically value different things in the workplace and will make different workplace choices based on their different preferences. Rather than simply putting forward the "nature" side of the debate, Browne suggests that dichotomies such as nature/nurture have impeded our understanding of the origins of human behavior. Through evolutionary biology we can understand not only how natural selection has created predispositions toward certain types of behavior but also how the social environment interacts with these predispositions to produce observed behavioral patterns.