Shooting American Family, Kentucky, By Carl Kiilsgaard

The diverse data coming from ethnography, history, law and social statistics, establish that the human family is an institution and not a biological fact founded on the natural relationship of consanguinity.
Early scholars of family history applied Darwin's biological theory of evolution in their theory of evolution of family systems. American anthropologist Lewis H. Morgan published Ancient Society in 1877 based on his theory of the three stages of human progress from Savagery through Barbarism to Civilization. Morgan's book was the "inspiration for Friedrich Engels' book" The Origin of the Family, Private Property and the State published in 1884.
Engels expanded Morgan's hypothesis that economical factors caused the transformation of primitive community into a class-divided society. Engels' theory of resource control, and later that of Karl Marx, was used to explain the cause and effect of change in family structure and function. The popularity of this theory was largely unmatched until the 1980s, when other sociological theories, most notably structural functionalism, gained acceptance.