The Sensitivity of Demographic Characteristics to the Strength of the Population Stabilizing Mechanism in a Model Hunter-Gatherer System

Abstract

In agent-based models of human systems where death and birth are represented, changes in population size are the result of the combined effects of mortality and fertility. If stability of population size is desired, these effects must be balanced. This paper investigates how the strength of a mortality-based feedback mechanism for constraining population size affects other demographic outcomes in a nonspatial agent-based model. The strength of the feedback mechanism is adjusted via a single parameter that controls the severity of the mortality penalty imposed when the population size exceeds a set threshold. Holding the values of all other parameters constant, I perform a set of experiments that sweeps through a wide range of values for the parameter and observe the effects on demographic outcomes such as mean household size, mean male age at marriage, mean percentage and intensity of polygynous marriage, mean total fertility, and mean inter-birth interval. Results suggest that the strength of the mortality-based feedback mechanism is positively associated with the range of variability in these outcomes, with the smaller population sizes produced by more severe constraints exhibiting a greater degree of variability in behaviors related to marriage, reproduction, and household size. The range of demographic outcomes remains within that documented in ethnographic cases.