Ancient Society
Already in his own times "Systems of Consanguinity" made a significant intellectual impact. Karl Marx read both "Systems" and Morgan's subsequent book "Ancient Society" (1877) which built on and extended the arguments of the previous one. Morgan's thought became foundational in Marx's development of his theory about the relation between evolution, social organization, and historical materialism. Posthumously, Marx' notes on Ancient Society were edited by Friedrich Engels and published as "The Origin of the Family, Private Property and the State".