The role of natural selection in evolution was formulated only a little more than a hundred years ago，and the selective role of the environment in shaping and maintaining the behavior of the individual is only beginning to be recognized and studied.

　　词汇突破：1.in evolution 在演化中

　　2.formulated 阐述；表述；解释；论证

　　3.shaping 形成（造就）

　　4.maintaining 保持，维护

　　5.recognized 认可，承认

　　主干识别：这里是两个并列句：

　　1. The role of natural selection was formulated.

　　2. The selective role of the environment is only beginning to be recognized and studied.

　　切分成分：only a little more than a hundred years ago 状语

　　in shaping and maintaining the behavior of the individual 状语

　　（注意：状语的位置一般在主语后，动词前。）

　　参考译文：自然选择在进化中的作用仅在一百多年前才得以阐明，而环境在塑造和保持个体行为时的选择作用则刚刚开始被认识和研究。

　　For the women of my generation who were urged to keep juggling through the 80’s, down-shifting in the mid 90s is not so much a search for the mythical good life--growing your own organic vegetables, and risking turning into a simpler, less materialistic lifestyle --as a personal recognition of your limitations.