Sentence:  One who comes to live in such a district does not separate his life entirely from the <WSD>autochthon</WSD> social reality, but the two realities, <WSD>autochthon</WSD> and immigrant, are not simple extensions of one another. In fact, there is a socio-cultural barrier behind which the <WSD>autochthon</WSD> population seeks protection from the colorful clusters of foreigners around it. 
Meaning of the word marked with <WSD> tags:  The earliest inhabitant of an area; an aborigine.