Why do you think the Stone Age people made such big graves for their dead?

I didn't know they did graves in the stone age but I do have a guess.

It was sorta the "stone age" they had to use it somehow.

i guess

Explanation:

"Why do you think" so it's an opinion

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.