The underlying reason for the eternal conflict between Republican "individual rights" and Democratic "we're all in this together" is explained by a radical and magisterial theory of evolution outlined in Edward O. Wilson's groundbreaking new book The Social Conquest of Earth. Wilson, who has dominated evolutionary thinking for the past 40 years, has synthesized a lifetime of work into a "theory of everything". Greatly simplified, his argument is that two rival evolutionary forces drive human behavior: first, individual selection, which rewards the fittest individuals by passing along their genes; and second, group selection, in which the communities that work best together come to dominate the gene pool. Wilson argues that these two evolutionary forces are at work simultaneously, so that both self-serving and altruistic behaviors are constantly competing at the individual and at the group level. As he explains, "Members of the same group compete with one another in a manner that leads to self-serving behavior .... At the higher level, groups compete with groups, favoring cooperative social traits among members of the same group." In other words, individuals with self-serving behaviors beat altruistic individuals, while groups of altruists beat groups of individuals with self-serving behaviors.
Extending this evolutionary theory, two competing forces are at work within the political organism: the "Republican genotype," which favors individualistic behaviors, and the "Democratic genotype," which favors altruism. Both forces are simultaneously at work at the individual and group levels. Different individuals -- and different groups -- will respond more or less to each of these forces depending upon the political and economic environment. The physiological differences between Democrats and Republicans in fear response, anxiety, etc., are simply symptoms of these competing genetic influences, and not the root cause of their divergent political beliefs.
Democrats and Republicans are not two sides of the same coin, but rather different parts of the same genome.
If this theory is correct, it should be applicable not simply to Democrats and Republicans but to political parties around the world -- that is, the general political structure of nations should split roughly into the "individualistic" versus "altruistic" models. In fact, most liberal democracies (i.e., where the voting is actually free and fair) have either a two-party system or a multi-party system having a dominant and a minority coalition, the two sides of which tend to split along those themes. In Britain, the Conservative Party argues for "putting more power in people's hands" while the Labour Party highlights "social justice and strong community." In France, the right-wing UMP (Nicolas Sarkozy's party) puts individual "liberty and responsibility" front and center, while the Socialist Party (of François Hollande) believes that social equality requires the "redistribution of resources and wealth." In Japan, the right-wing Democratic Party "values people's individuality and vitality," while the left-wing Liberal Democratic Party begins its constitution with a call for the "prosperity of mankind."