Okay, so this footnote is correct and evidenced but it also sounds overtly feminist: The trait in evolutionary biology is that women put each other down because establishing a better position in the heirarchy gives us the choice of a higher standard man (women choose with whom to settle; men choosing is a myth we allow their egos to assume). Being catty provides an advantage in natural selection, although it also loses friends. Read Maynard Smith on The Evolution of Sex.