In my universe, there are sixteen species from the Homo genus: anatomically modern humans, marine humans (merfolk), winged humans (angels), demons, ogres, giants, dwarfs, elves, orcs, gnomes, trolls, goblins, halflings, furry humans (therianthropes), hematophagous humans (vampires), and magical humans (wizards). Some of them prefer monarchies, others prefer republics, some prefer statist/authoritarian/totalitarian states, others prefer liberal/libertarian/anarchist states.
- Most countries mostly populated by anatomically modern humans are democracies (of various types).
- Merfolk live in a matriarchal, matrilinear, federal, constitutional, and elective monarchy (an empire to be exact: the Head of State is the Empress, and the equivalents to American governors are the seven Queens).
- Angels live in a patriarchal but matrilinear theocracy ruled by four celibate priests.
- Demons live in a matriarchal but patrilinear, absolute, and hereditary monarchy.
- Ogres live in a matriarchal, matrilinear, and tribal society (if someone wants to be the Big Chief, she must win a wrestling tournament, but, there is distribution of power).
- Giants also live in a matriarchal and matrilinear tribal society (there are both elections and distribution of power).
- Dwarfs live in a patriarchal, patrilinear, presidential, unitary, and hereditary republic (a hereditary republic means the title of president is passed to the son of the ruler when he dies like Haiti's Duvalier dynasty, except that they have limited power instead of being despots).
- Elves live in a patriarchal, patrilinear, federal, constitutional, and elective triarchy (a principality to be exact).
- Orcs live in a warrior state à la Genghis Khan.
- Gnomes live in a patriarchal, patrilinear, and tribal society (there are elections, but no distribution of power).
- Trolls live in a patriarchal, patrilinear, and tribal society (the title of Big Chief is hereditary, but there is distribution of power).
- Goblins live in a Singapore-like benevolent dictatorship.
- Halflings live in a patriarchal, patrilinear, parliamentary, federal, and elective republic (except there are three presidents and three prime ministers simultaneously) (this is comparable to ancient Rome).
- Therianthropes live in a Somalia-like anarchist state.
- Vampires live in a matriarchal but patrilinear, unitary, absolute but elective monarchy (a kingdom to be exact).
- Wizards live in a matriarchal and matrilinear theocracy with an Indian-like caste system (except that priests and priestesses can marry and have children, either biologically or by adoption).
So, I wonder why would each species from the Homo genus have a different preferred political system.