Evolution is natural gradual process of development in accordance with the needs of natural world. As environment in the nature transforms, it demands only species to survive that can fit. In other sense is modification process to survive in the natural world is genetic evolution. 

Environmental process by occurrence changes condition for species, evolution process acts accordingly for existence. Reacts and modifies shapes to fit in the environment. Environment initiates species to react for its fittingness. All genuses do not survive due to incompatibility; on the other hand which is strong to endure can survive or modify selves to fit with. Nature wants something new and evolution given it.

History & social evolution: Evolutionary process of cultures and religions enhance its population to rise and go along. This process of evolution passes from individuals to entire society to make strong society. Those societies which are not strong  either subside or merge with the strong one. This way the civilization prolongs till reaches to its highest point and starts decomposing as the rule of universe is extreme of positive gives birth to negative and extreme of negative gives birth to positive. Means its extreme starts rotting and begin to collapse. Can be a cause by either natural (overheating earth, earth quack, famine etc ;) or human created disaster, deforestation converting to desert, polluting nature to disturb ecosystem, extreme practices. Its extreme practices to maintain its civilization gives birth to new form of revolution to start new liberal community thus the old one becomes history of civilization and new one is the evolutionary form. Present civilization will also have the same consequence; present affect of this civilization is extreme poverty, rotten attitude of religions, and extremism etc; are changing the environment when reaches to extreme will begin revolution to evolve.