難句解析：
①There are about 105 males born for every 100 females, but this ratio drops to near balance at the age of maturity, and among 70-year-olds there are twice as many women as men.
▲該句是由三個遞進關系的簡單句組成的并列句，句法結構比較清晰。
△第一個分句的關鍵詞在born，表明該比數是嬰兒出生時的性別比例；第二個分句的關鍵詞在near balance（接近持平）和at the age of maturity，表示性別比例的持平狀態發生在成年時期；第三個分句的70-year-olds指代的是“70歲的人們”，作名詞。
②Again, differences between people and the opportunity for natural selection to take advantage of it have diminished.
▲注意differences between people和the opportunity for natural selection to take advantage of it是兩個并列的主語，千萬不要理解成people與the opportunity是between的并列賓語。
△and連接的兩個并列部分是differences between people和the opportunity for natural selection to take advantage of it，而不是people和the opportunity。另外注意句中的it指代的是differences between people。
③The grand mediocrity of today — everyone being the same in survival and number of offspring — means that natural selection has lost 80％ of its power in upper-middle-class India compared to the tribes.
▲該句的主語是The grand mediocrity，謂語是means，其后跟著that引導的賓語從句that natural selection has lost 80％ of its power in upper-middle-class India compared to the tribes，其中compared to the tribes是分詞結構作狀語，省略了if/when being。破折號中間everyone being the same in survival and number of offspring是典型的插入語，其中survival和number of offspring都是介詞in的賓語。
△grand在此處不是“宏偉，壯麗”的意思，而是“程度很深”；mediocrity也非“平庸，平常”，而是“平均化”或“折衷”；offspring是“后代”。另外要理解natural selection has lost 80％ of its power in upper-middle-class India的意思，這里是指在原來的社會不平等的情況下，印度中上層階級擁有一些能使自己在自然選擇中處于優勢的特權，而隨著醫療和衛生條件的改變，下層人民也擁有同樣的生存條件，因此中上層階級就喪失了80％的自然選擇中的優勢。
④Darwin had a phrase to describe those ignorant of evolution: they "look at an organic being as a savage looks at a ship, as at something wholly beyond his comprehension."
▲冒號后的句子是主句中a phrase的同位語。該同位語從句中的結構是A does something as B does something（A做某事的樣子正像B做某事的樣子）。
△those ignorant of evolution指對生物進化過程一無所知的人，其后的they也指代這些人。最后的his指代前面的a savage。beyond his comprehension超出了他的理解范圍。
來源:可可英語 http://www.ccdyzl.cn/kaoyan/201406/304431.shtml