Clans are fundamental. It is but another way to say kin group or tribe
To call the descendants of transatlantic slavery clannish is a joke. Their ethnic identities are formed in response to how non blacks treat them. You go to those majority black islands in the Caribbean and they hardly ever discuss race. It is in Guyana and T&T that it becomes an issue because blacks in those two nations feel a vulnerability that they don't in Barbados.
Go to the DR and someone like Denzel Washington will have a meltdown if you called them black. So what kind of racially based clannish loyalties do we have? You have 1/3 of the "black" population of Guyana, who would be called mixed if they went to Barbados, calling themselves mixed. Yes people like Raphael Trotman and Mark Benschop.