In this paper we use the cross-cultural record to identify the behavioral rules of conduct, and the system supporting those rules, that are found in traditional societies, such as tribal societies. We then draw on the historical record to identify the behavioral rules of conduct, and the system supporting those rules that were found in the early state. The proposal tested here is that in traditional societies the behavioral rules of conduct and the systems that support them (e.g., processes for identifying guilt, punishing offenders, enacting legislation, preventing conflict) are aimed at promoting enduring, cooperative relationships among individuals who are identified as kin through common ancestry. The assumption underlying this proposal is that once human females increased their investment in offspring, cultural strategies to protect those offspring became more important. A moral system, which is the term we use to refer to the early system of behavioral codes, protected offspring by turning conspecific threats into the protectors, providers, and educators of children. It did this by creating a strong kinship system, the members of which were bound by common ancestry (actual or metaphorical), thus tying individuals into enduring, cooperative relationships by using culture to encourage them to honor ongoing duties to one another. This kinship-based moral system is significantly different from that found in societies in which the majority of interactions are with non-kin, interactions often center on the exchange of good and services, and traditions have largely been broken down. We refer to this second system as a system of law and argue that this distinction between moral and legal systems has implications for attempts to explain the evolutionary basis of human cooperation.

Kinship has often been referred to as the heart of anthropology because societies are woven together by genealogical ties. In this paper we present a general model of the effect of the tradition of marriage on the potential number of individuals that can be identified as kin. The exact amount of increase in the number identifiable kin depends on demographic variables, but it will always be greater than the mere doubling of kin that might be first assumed. It is our hope that this model will stimulate discussions over whether or not such an increase in identified kin might have been important to human evolution, and if so, in what way and under what circumstances. Such discussions may help bridge the gap that has been created between those anthropologists who see kinship as fundamentally biological and those who see it as a purely cultural phenomenon.

Anthropologists often recorded the typical amount of kinship altruism – that is, the altruism between individuals who identify one another as kin -- they observed in what they referred to as tribal or traditional societies (e.g., Murdock 1949; Keesing 1975; Fortes 1969; Evans-Pritchard 1940). This altruism, they noted, was extended to very distant kin. This altruism toward distant kin, as several scholars have pointed out (E. O. Wilson, D.S. Wilson), is fundamentally inconsistent with the predictions of kin selection. In this paper, we present a possible solution to this puzzle, and one that does not reply on group selection. To do this we introduce a new evolutionary concept called “ancestor-descendant conflict” and the mathematical formula upon which it is based. The concept of “ancestor-descendant conflict” is a multi-generational diachronic extension of Trivers’ concept of “parent-offspring conflict.” It leads to an extension and revision of Hamilton’s rule “C