the works of Leslie White and Lewis Henry Morgan, developing the ecological-evolutionary theory. He views technological progress as the most basic factor in the evolution of societies and cultures. Unlike White, who defined technology as the ability to create and utilise energy, Lenski focuses on information—its amount and uses. The more information and knowledge (especially allowing the shaping of natural environment) a given society has, the more advanced it is. He distinguishes four stages of human development, based on advances in the history of communication. In the first stage, information is passed by genes. In the second, when humans gain sentience, they can learn and pass information through by experience. In the third, humans start using signs and develop logic. In the fourth, they can create symbols and develop language and writing. Advancements in the technology of communication translate into advancements in the economic system and political system, distribution of goods, social inequality and other spheres of social life. He also differentiates societies based on their level of technology, communication and economy: (1) hunters and gatherers, (2) agricultural, (3) industrial, and (4) special (like fishing societies). Talcott Parsons, author of Societies: Evolutionary and Comparative Perspectives (1966) and The System of Modern Societies (1971) divided evolution into four subprocesses: (1) division, which creates functional subsystems from the main system; (2) adaptation, where those systems evolve into more efficient versions; (3) inclusion of elements previously excluded from the given systems; and (4) generalization of values, increasing the legitimization of the ever more complex system. He shows those processes on 4 stages of evolution: (I) primitive or foraging, (II) archaic agricultural, (III) classical or "historic" in his terminology, using formalized and universalizing theories about reality and (IV) modern empirical cultures. However, these divisions in Parsons' theory are the more formal ways in which the evolutionary process is conceptualized, and should not be mistaken for Parsons' actual theory. Parsons develops a theory where he tries to reveal the complexity of the processes which take form between two points of necessity, the first being the cultural "necessity," which is given through the values-system of each evolving community; the other is the environmental necessities, which most directly is reflected in the material realities of the basic production system and in the relative capacity of each industrial-economical level at each window of time. Generally, Parsons highlights that the dynamics and directions of these processes is shaped by