Carrying capacity, cycles, and culture

Abstract

Two major objections have been made to the application of the "carrying capacity" (K) concept to nonindustrial human populations: 1) If K is set by periodic famines or other phenomena ("minima"), the concept is useless without an independant criterion for the length of the relevant period. 2) Humans frequently appear to be adjusting their population densities according to what seem to be biologically arbitrary cultural criteria, not to a biological K. I propose that the length of the relevant interval between minima is a function of the species' pattern of investment in kin. Minima occuring at intervals greater in length than the period of investment will have little effect on reproductive tactics, and intervals shorter in length than the period of obligate offspring dependancy are roughly equivalent biologically. This conclusion should apply to all "K-selected" species. For humans, minima at intervals of up to about 50 years may determine K for a population. I suggest that "arbitrary" preferences that limit population growth are in fact culturally selected traits that stabilize populations at Ks set by these minima. Cultural, rather than genetical, selection allows human populations to track relevant minima through environmental shifts such as ice ages.