Poltical Philosophy, Organization, Human Mutability

A Political Philosophy tends to propose a best system, typically presupposing some fixed, perhaps a priori, characteristic of Humanity.  However, the ample evidence is of conditions that have been varying over the centuries, not only insofar as the fundamental unit of organization has grown from City to Nation, and, perhaps, to Global Community, but also insofar as, especially more recently, technological advances have drastically altered the capacity for communication that is a factor in such organization.  Furthermore, not only do conditions vary, but if Marxism and Darwinism, for example, are correct, such variation is indicative of an inherent mutability of Humanity itself.  So, beyond the fundamental principle of Political Philosophy--that collective organization is better than its lack--further specification seems contingent.