nor do they seem likely to become so. Recently [1963] some Brazilian Catholic social scientists compared their country's progress with that of the United States and concluded that the chief factor responsible for the differential rates of development is the religious heritage of the two nations." Ecological-evolutionary theory In subsequent publications (Power and Privilege, 1966; Human Societies, 1970; and Ecological-Evolutionary Theory, 2006), Lenski built on the foundations of evolutionary theory laid in the 18th century by A.R.J. Turgot, Adam Ferguson, John Millar, and Thomas Malthus, and in the 19th and 20th centuries by Charles Darwin, Lewis Henry Morgan, and Leslie White and the many biological evolutionists following him, to propose a more contemporary ecological and evolutionary theory of societal development from the Stone Age to the present. He has viewed the cumulation of information, especially technological information, as the most basic and most powerful factor in the evolution of human societies (though not the only one, as some of his critics have claimed). Lenski has argued that the evolution of cultural information is an extension of the evolution of genetic information with the characteristics of human societies being the product of the interaction of both genetic and cultural influences. Members of any given society are united by a shared and partially distinctive culture and networks of social relationships with one another. These ties vary in intensity and distinctiveness depending on the magnitude of the society's store of information and the extent of contacts with other societies. With the acquisition of signals, and later, symbols, the ancestors of modern humans gained the critically important ability to share information acquired through individual experience. These and other later advances in the technologies of communication and transportation laid the foundations for major developments in political and economic systems, social inequality, science, ideology, and other spheres of life. Lenski's theory has been well received. A former president of the American Political Science Association, Heinz Eulau, described Power and Privilege as a "masterpiece of comparative social analysis" and Ralf Dahrendorf referred to it as "an imaginative and substantial work [and] an indispensable guide." Sociological Theory devoted an issue of the journal to commentaries on, and appreciations of, his work (vol. 22, no. 2, June, 2004). One feature of Lenski's work that has won fairly wide acceptance among sociologists, as reflected in its incorporation into leading introductory textbooks in the discipline, is his ecological and evolutionary typology