Five Cultural and Natural Checks on Population Growth.

Concluding thoughts in this essay are that modern man is capable of adjusting population size to the level of economic development or "allowing Nature to adjust by genetic provisions which are valuable in mans evolution but are insensitive and amoral." Population numbers can be adjusted without involving distress and unhappiness. A review is provided of animal behavior studies which enlighten the understanding of self-regulatory mechanisms of overpopulation. The Malthusian notion that annual survival is dependent on current food supply is unsupported by studies of natural animal populations. The amount of food appears not to limit the growth of animal and human populations. Chitty and Lack reveal that population density and food shortages may be corrected in many ways and in balanced reproduction in succeeding generations. Patterns of periodic population decline may mimic predator-prey cycles. Suicidal mass wanderings of lemmings appear in 3-4 year cycles. There is also evidence of congenital damage from pregnancy period stress. Calhouns rat populations under stress from overpopulation changed social behavior in such ways as to create subdivisions within groups challenges to the dominant hierarchy which led to unstable groups and reduced conception and more frequent attacks on the young. The shock state can persist into several generations. Survival also appeared to be related to defense of territory viability of the young and genetic propensity for malformation. Human populations are limited by cultural practices such as infanticide and circumcision in infancy. Human populations have been shown to exhibit increased illness of offspring associated with pregnancy stress and emotional upset. There are many parallels between human stress responses and animal behavior deterioration and population declines.