The kinship web in a simple stationary population

Robert Schoen


A basic feature implicit in all populations is the kin structure and the number of kin of different kinds that individuals have over their lifetime. We begin with a very simple model where all persons survive to exact age 90, and at exact age 30 every person has two children, one boy and one girl.  If the population size is 4n+2 persons, every person can marry another no closer in kinship than an (n−1)st cousin, with the kinship web reproducing itself across generations. Over each person's life cycle, the number of kin within the fourth degree of kinship (e.g. first cousin) varies between 13 and 20. That number of kin increases substantially if fertility doubles and contracts if life expectancy is reduced to 60 years (2 generations). Since the figures do not include our reference person Ego's spouse or spouse's kin, even a stationary population with a two generation lifespan appears capable of supporting extensive, kin-based social relationships.


Robert  SCHOEN, Senior Scholar, Department of Sociology and Affiliate, Population Research Institute, Pennsylvania State University, University Park PA 16802 (USA). E-mail:


kinship; stationary population; life cycle; consanguinity; degree of relatedness

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ISSN: 2035-5556

Reg. Tribunale di Roma n. 3321/54