抄録
There are more than 300 species of primates, including human beings, on earth. Human beings share various characteristics such as morphology, physiology, ethology, and sociology with other primates. Primates have a common ancestor, and so a common evolutionary history. Various social units formed in primate societies exhibit a range of behaviors including monogamy, polygyny, polyandry, and multi-male/multi-female relations. Among all primates, however, only humans have a social “family” unit. The family is defined as a small-scale kin group consisting of a husband, a wife, and a child. This is the smallest social unit in human society, and it is found in almost all human societies. How would this social unit, unique to humans, have been formed? Johanson and White (1976) discovered the fossilized remains of Australopithecus afarensis, the Hominidae, who lived 3.75 million years ago, in Hadar, Ethiopia. These fossils were found to be a lineal ancestor to the human race, and were named the “first family,” because the fossils of 13 individuals (both sexes, including children) were excavated from the same ruins. However, the first family's behaviors and societies were not fossilized. Development of the family unit was a dynamic process, and therefore it is only speculation that human evolution resulted from a group of close relatives who had in turn evolved from a common ancestor. Imanishi (1951) identified four conditions necessary to a human family as being: 1. a taboo against incest, 2. exogamy, 3. community, and 4. the division of labor. I would like to discuss the origins of human society by comparing our closest relatives, the society of apes, to the four conditions Imanishi described as necessary to a human family.
