The rural workforce has been flowing in to the cities ever since the open door policy was adopted.
自从改革开放政策实施以来,农付劳动力正不断流向城市。
It is thought that they arrived more than 30,000 years ago by crossing a land bridge from Asia to America.
他们被认为是在3万多年以前从亚洲跨越一座陆桥来到美洲的。