Men are wired to jump into that lust stage of attraction very quickly, the physical stage. Men still also have really high levels of testosterone, which apparently blocks the release of oxytocin in their brains. Once men evolve to the romantic attraction phase, their brains release oxytocin more associated with commitment and certainty. When a man commits his testosterone is no longer blocking the release of Oxytocin so they can fall in love and develop a long term bond.