"Unitary democracy almost certainly has a longer history than any other form of government. For more than 99 percent of our existence, we human beings lived in hunter- gatherer bands. We know relatively little about these bands in earlier times. What we do know suggests a remarkable degree of economic equality in them. More recent evidence suggests a comparable degree of political equality. At least in the past few centuries, these groups have habitually made their decisions as equals, by consensus, and in face- to-face meetings. It seems fairly safe to infer that hunter- gatherers always operated as unitary democracies.
In modern bands, each adult male comes to the band's decision-making council as an equal. Some bands have no head at all; others select an older man to act as a peacemaker and arbitrator in the council, not to hold a higher rank or exercise any formal power. This fundamental equality in status does not necessarily imply equal influence on decisions. The opinions of an individual who combines skill in hunting and in warfare with the personal qualities of generosity, kindness, self-control, experience, and good judgment may well carry more weight than those of other men. But the influence of such a man does not derive from a position of formal authority, entails no obligation on the part of other members of the band, and is not accompanied by any marks or perquisites of higher status.
The unitary approach of these bands assumes that the band as a whole has a common interest. But only very small societies can make this assumption and can maintain this kind of decision- making. With increasing membership, the probability of a groups' achieving a common interest, and therefore genuine consensus, diminishes rapidly. The participants in a large polity may never meet, and if they do, they will usually know each other in only one role, often one that dramatizes conflicts of interest. Large-scale organization also requires a hierarchy of some sort, if only for communications. Finally, sheer numbers make impossible a face-to-face meeting of all members at once. For these and other reasons, unitary democracy has had no large-scale form.
When large-scale polities first developed, they retained the central ideal of common interest while scrapping the democratic paraphernalia of equal status, consensus, and face-to-face assembly. In chiefdoms, monarchies, and even empires, one individual often personified the whole, becoming a unifying force in the face of increasingly diverse interests. The authority structure in these unitary, but nondemocratic, polities mirrored that of hunter-gatherer families rather than that of hunter- gatherer councils. Large- scale democracies had to await the full development of a theory of adversary democracy."
"The unitary approach also has its limits. No group of people, however small, ever has completely identical interests. But groups whose members have many common interests often develop norms that make it difficult even to suggest that individual interests might conflict. Groups that are accustomed to using consensus find it hard to recognize and to legitimate conflicts of interest by allowing bargains, distributing benefits proportionately, taking turns, or making decisions by majority rule. Such groups end up either reinforcing the status quo or, in an informal and unacknowledged manner, forcing the minority to go along.
The larger the polity, the more likely it is that some individuals will have conflicting interests, and the more individual interests come in conflict, the more a democracy must employ adversary procedures. These two premises demand the conclusion that democracies as large as the modern nation-state be primarily adversary democracies.
This is a bitter conclusion. It means rejecting the vision of national unitary democracy where interests coincide naturally, through unselfishness, or through the power of an idea. The unitary vision appeals to humanity's most exalted sentiments - the deep joy of spontaneous communion, unselfishness, and commitment to a larger good. When a powerful ideal or moment of transcendence unites millions of people, the result is even more inspiring than in a small community. Yet on this scale, the unitary goal is also more dangerous, because with increasing size the chances of real conflict increase, and so, consequently, do the chances that an appeal to unity will obscure conflict to the benefit of those who launch the appeal.
The depressing conclusion is that democratic institutions on a national scale can seldom be based on the assumption of a common good. Yet a democracy based solely on the cold facts of national conflict will encourage selfishness based on perceiving others as opponents and discourage reasoned discussion among people of good will." (http://www.context.org/ICLIB/IC07/Mansbrdg.htm)