I know this is a post on Christianity, but here is something from the Qur'an that talks about what you referred to.

010.047
YUSUFALI: To every people (was sent) a messenger: when their messenger comes (before them), the matter will be judged between them with justice, and they will not be wronged.
PICKTHAL: And for every nation there is a messenger. And when their messenger cometh (on the Day of Judgment) it will be judged between them fairly, and they will not be wronged.
SHAKIR: And every nation had a messenger; so when their messenger came, the matter was decided between them with justice and they shall not be dealt with unjustly.

>Wouldnt He supply each
>culture, geographic area, etc with
>Many books of truth?