It is probably uncontentious by now to assert that a code of behaviour evolved during the development of the human social group, to enable individuals to function with each other and as part of the group. Since it is hard to imagine that any very sophisticated interaction could have taken place in the group until the emergence of language, it is perhaps also reasonable to date the availability of a set of 'groupish' moral templates to the same period. Little change can have taken place to the genetic inheritance of modern man since then, so we can assert that the genetically-embedded moral structure of humans is at least 250,000 years old.
Many commentators locate the emergence of complex social interaction in the hunter-gatherer group, comprised of men (in most cases) who separated out from the undifferentiated, mixed kin-group, and needed to develop sophisticated techniques for co-operation and communication. This may explain why it was through 'The Fathers', or the male elders of the tribe, that law emerged as the basis of all conduct, moral or otherwise. The feminine emancipation of the last 150 years has shifted the law into the hands of women as equal partners alongside men, but the masculine origins of the law are hard to dispute.
De Jouvenel 1 describes the omnipotent legal powers exercised as of right by individual male heads of tribes (families, kin-groups) in Ancient Rome, and jointly by male councils, quoting Maine 2 in support of this depiction. It is difficult to doubt that the supremacy of male members of early tribes (groups) stems directly from the role of 'the Fathers' in early human groups, however this is thought to have originated.
For rules of conduct to be more than pious aspirations on the part of the more reflective members of a group, there also needs to be a propensity to accept such rules among all group members, and it is clear that this propensity did develop alongside the rules themselves.
Inside the human group there is very strong pressure for conformity – what is loosely referred to, often pejoratively, as the 'herd' instinct. It's obvious that the group would seek to impose conformity on its members in many respects (although dissent is adaptive when it comes to competition between groups, because it allows for greater flexibility of group behaviour). It's also obvious that one of the best ways of ensuring conformity (after mimetics) is by reference to an objective body of rules (or morals or laws) which all members of the group accept. It's not difficult to see how 'the law' would have evolved as a mechanism for ensuring group solidarity, initially through 'The Fathers' and later on as a separate body of rules independent of any particular sub-group, although there would always be a sub-group (or groups) with devolved responsibility for maintenance and enforcement of the rules. Today, the judiciary and the police are those groups; in the hunter-gatherer group, it was the Fathers, and perhaps even they had 'heavies' at their disposal (in return for extra meat?).
Peter Kropotkin 3 emphasizes the long continuity of village- or community-based law in Europe and Russia, throughout history and up to the 15th century. Such law is very centered on individual relationships within the group, on solving problems in the group, on assessing 'right' and 'wrong' as between people and dealing with compensation. However, at all times the individual is treated as being part of the group, and the actions of an individual are treated as actions of the group.
'Every quarrel arising between two individuals was treated as a communal affair – even the offensive words that might have been uttered during a quarrel being considered as an offence to the community and its ancestors. . . . The judicial procedure was imbued with the same spirit. Every dispute was brought first before mediators or arbiters, and it mostly ended with them, the arbiters playing a very important part in barbarian society. But if the case was too grave to be settled in this way, it came before the 'folkmote', often in a jury setting.'
Kropotkin remarks upon the persistence of this community-based customary law even after villages had come under the sway of warlords. 'The moral authority of the commune was so great that even at a much later epoch, when the village communities fell into submission to the feudal lord, they maintained their judicial powers.'
Kropotkin also notes that the death penalty, indeed all penalties, were scarcely available under customary law. If a person was unable to pay compensation, even for killing, he would normally join the family or group of the injured party.
It is not right however to suppose that members of primitive tribal societies obeyed their folk-laws purely out of a sense of moral obligation to the group. There were sanctions which could be applied if they did not, ranging from expulsion (a serious and possibly fatal punishment) to violent retribution from relatives of injured individuals. Evans-Pritchard 4 makes this clear: 'What chiefly makes people pay compensation is fear that the injured man and his kin may take to violence . . . also the chances of a man obtaining redress for an injury are less the further removed he is from the man who has injured him, since the opportunity for violence and the effectiveness of kinship backing lessen the wider the distance between the principals.'
Richard Alexander 5 says that rules of morality and law seem to be designed to enable societies to be sufficiently united to deter their enemies rather than just to allow people to live in harmony within societies. But that is surely too limiting: a group has a competitive advantage if it has a set of agreed-upon rules, but that doesn't prevent the rules from achieving other goals – division of labour between men and women, efficient hunting and so on.
De Jouvenel contrasts 'law', or at least the process of 'legislation', coming at a relatively late stage of human societal development, with the body of customs and moral precepts, seen as being fixed from time immemorial. He quotes Westermarck 6: 'The Rejangs of Sumatra do not acknowledge a right in the chiefs to constitute what laws they think proper, or to repeal or alter their ancient usages, of which they are extremely tenacious and jealous. There is no word in their language which signifies law.'
During the Middle Ages and the Renaissance, church law took on much of the ethical burden of society; but customary law continued to exist in parallel with church law, and with commercial law as expressed by the guilds. All were equally distant from the emerging State, whose legal competence at that stage was limited to some aspects of what we would today call criminal law. Churches had their own courts (and still do, although in places other than the Vatican and in Islamic countries they nowadays have extremely limited powers). Customary law at village and town level was administered by local officials and was during that period no concern of central government.
De Jouvenel, B (1948) On Power, tr J F Huntingdon, Hutchinson, London (originally published in French in 1945)
Maine (1861) Ancient Law: Its Connection With The Early History Of Society And Its Relation To Modern Ideas, London
Kropotkin, P (1902) Mutual Aid, Heinemann, London
Evans-Pritchard, E E (1940) The Nuer; A Description Of The Modes Of Livelihood And Political Institutions Of A Nilotic People, OUP
Alexander, Richard (1987) The Biology of Moral Systems, Aldine De Gruyter, New York
Westermarck, (1906) The Origin and Development of the Moral Ideas, Vol I p 162, Macmillan, London