Migration

Before Mao's Cultural Revolution, the Orogen people were nomadic hunters.  They'd travel the forests of Inner Mongolia calling no single part home, but forever moving.  Their whole life and culture was primarily based around hunting, but after the Cultural Revolution, bans were placed on hunting.  This lead to a drastic change in the Orogen lifestyle.  They were forced to leave the forests and abandon their old ways for new ones.  Leaving the forests of Inner Mongolia, many Orogen moved toward more rural areas, or places to farm.  It is very similar to the U.S. Industrial Revolution; farmers moving up north toward urban areas.

http://english.sina.com/china/p/2008/1229/207949.html

http://www.china.org.cn/english/features/EthnicGroups/136942.htm