Alpha males are perceived as domineering leaders who are driven by a desire for prestige and attention.  In contrast, sigma males deny the need for external validation.  Although they are both self-assured and competent, sigma meaning is that a male who prefer to work alone and autonomously.  They do not follow social hierarchies rather than attempting to control or conform to them.  What distinguishes them is this remoteness.  Whereas Alphas guide teams, Sigmas choose their own route, which makes them enigmatic and frequently more surprising in their achievements.