The apology david lurie presents to the isaac family can be seen as a display of:

the factors that the economies of the muslim empires prosper were:

1- land trade routes-located between three continents  

2- sea trade routes

trade contributed to the spread of muslim empires, and with that islamic culture led to a growing feeling of internationalism resulted in the transfer of technology, science, and other cultural forms.

the answer to your question is,

old stone age.

-mabel < 3