从猿逐步进化为人

постепенная эволюция из обезьяны в человека

逐步积累的渐进过程

gradual, cumulative process

先搞试点，进而逐步推广

first make experiments at chosen units and then extend its application step by step

分批进入和退出的逐步回归法

in-and-out stepwise method