People: The Quantity and Quality of Population

achievements actual American animals average basic basis behavior biological birth control birth rate births and deaths breeding cause census century characteristics civilized death rate desire economic culture effect environment equipment eugenicists eugenics existence fact factors future germ plasm given growth of population habitat heredity human population human species immigration important improvement individual infant mortality intelligence land larithmic level of living limited logistic curve Malthus mankind marriage married couples material mating means ment modern nation natural increase negative eugenics nomic obviously offspring optimum organic overpopulation ovum parents period persons physical popu population growth possible practical present probably problem procreation production question rate of natural reason represents reproduction result Sanger scientific situation social society standing room stationary statistics sub-human supplies tend tendency things tion traits underpopulation United vidual vital women zygote