Earlier quoted context omitted.
Oh yes you can: men have testosterone, so they're more aggressive, which turns out to translate to asking for more pay raises more often and changing jobs more quickly if unhappy with their pay. Hey presto, a biological basis for unequal pay. Now obviously this doesn't explain everything about unequal pay -- but it would be foolish to ignore entirely, no?
Nurture can trump nature, though: There are matrilineal societies where competitiveness is considered a feminine trait. As is often the case, it's not simply either/or.
> We cannot hope to understand sex and gender until we clarify our attitude toward nature. Sex is a subset to nature. Sex is the natural in man.
She's not saying that biology is the sole factor that determines how we behave. She's saying that we need to understand it and integrate it into our understanding of cultural, psychological, sociological artifacts. Or more importantly, we can't understand them without taking into account biology. I don't see anything wrong here.