Both the admiralty and the captains (regularly) featured on Star Trek are, to my knowledge, all human. Isn't this odd, for an organisation priding itself on including as many different species as possible? There are plenty examples of non-human first officers (Keira on DS9, Spock and T'Pol, to name a few), far fewer of captains.
Are there non-human captains in Starfleet? How about admirals / commodores? Are humans over-represented in the higher echelons?