Members of monkeys (primates) were pioneer mammals which utilized abundant forest resources on a full scale. Tree tops with thickly growing branches and leaves are ideal places to inhabit where there are very few predators andcompetitionis less severe. The ancestors of modern day monkeys developed various body structures and living styles,resulting in clear division into various types.They expanded their living areas from forests to savanna and desert, and acquired the necessaryliving techniques according to the particular nature of the environment. During the course of these developments, human ancestors came to appear.