Steven Pinker book The Blank Slate
p. 485 http://books.google.com/books?id=ePNi4ZqYdVQC&q=%22humans+are+interchangeable%22 <br class="br">The Blank Slate (2002) <br class="br">Source: The Blank Slate: The Modern Denial of Human Nature <br class="br">Context: [E]quality is not the empirical claim that all groups of humans are interchangeable; it is the moral principle that individuals should not be judged or constrained by the average properties of their group. … If we recognize this principle, no one has to spin myths about the indistinguishability of the sexes to justify equality.