先分析下这句话的结构：
The world 是主语；peppered with 是谓语动词,且是过去时；languages spoken by a few people 可以说整个都是宾语,但其中spoken by a few people 是做languages的定语.
原句可以还原成：The world peppered with languages that is spoken by a few people.后面就是一个定语从句了.因为speak ,即定语从句中的谓语动词和先行词language的关系是动宾关系,即speak languages,所以从定语从句变为短语时,采用被动,即languages spoken by a few people.
注意,如果先行词和从句中的谓语动词是主动关系,变为短语是采用主动.