For the most part, it is not the nature of women to use men for protection, resources, and, in the case of her interaction with alpha-males, reproduction. The main reason behind this is not their physical vulnerabilities. Manipulation is not the best word to use to describe this mechanism because it presupposes a degree of maliciousness or intentional deception and it's not useful in that it suggests women are instinctively tricky with respect to the value they advertise versus what they actually provide in an interaction pattern not deliberately calibrated by a more-manipulative, intelligent, and self-interested male.