Several posters have already said that the question of Sharia law is better suited for a religion sub.
In fact, the question of how law codes arise out of religion and are influenced both by religion and culture (and how religion and culture are intertwined) is a perfectly legitimate avenue of historical inquiry. A religion sub would, of course, have its own perspective, but that doesn't mean the question can't be answered here.
So please, if you're coming here to tell the OP to go elsewhere, don't.
/u/Snowchill: You may be interested in some of these previous posts about Islam, while you wait for an answer from an expert:
http://www.reddit.com/r/AskHistorians/comments/1ych3d/ama_modern_islam/
Sharia law is at a very basic level a collection of opinions given out by an enormous number of Islamic scholars over the course of Islam's history. It is not monolithic, and it is not a handbook of barbaric practices as it is sometimes portrayed. Think of it as being somewhat akin to the Talmud or especially to the common law.
It has had more than a thousand years to develop and evolve, differs in interpretation from one time and place to another, and during that time opinions have been issued that cover everything from riparian rights to workplace health and safety. Precedents may or may not be binding depending on where you are, and the importance or currency of a decision often depends on the reputation of whoever offers the opinion and his quality of scholarship. The folks over in /r/Islam can be of some assistance to you, and if you are curious about the similarities between Sharia and other legal systems, ask them.