Charles Darwin (1876/1958), from his autobiography states that some fifteen moths after beginning his inquiry he read Malthus on population, "it at once struck me that under these circumstances favorable variations would tend to be preserved, and unfavorable ones to be destroyed,  The results of this would be the formation of a new species.  Here, then I had at last got a theory by which to work."

Alfred Wallace (1905) also reports in his autobiography that "perhaps the most important book I read was Malthus' Principle of Population...its main principles remained with me as a permanent possession, and twenty years later gave me the long-sought clue of the effective agent in the evolution of organic species."

Gerhard and Jean Lenski present an evolutionary-ecological theory as an integrating device, synthesizing both the classical works of sociologists and anthropologists and contemporary social theory and findings.  In their acknowledgments to their 5th edition of Human Societies, the Lenski's acknowledge their debt to many social scientists, Malthus being the first among them (1987: xv).  The Lenski's present an ecological-evolutionary theory of social organization and change that is profoundly influenced by Malthus.
 

Malthus' Social Theory