What is the theme in The Red Queen: Sex and the Evolution of Human Nature by Matt Ridley?

Nature versus nurture is a theme. Since Rousseau, a debate has raged in social sciences over whether human nature is the product of heredity, nature, or nurture. After Charles Darwin's theories grew popular, it became accepted that nature was responsible for many human traits. The crimes of eugenicist and racists who used pseudo-biology in pursuit of their fascist aims provoked a backlash in the late 20th century. Scholars taking a cue from Durkheim and Marx, argued that almost nothing was the result of nature and that there were no real biologically-based differences between persons. It grew apparent that these scholars were intent on advocating egalitarianism through their work. Hence it was absolutely necessary that humans being not be different biologically.