To answer your question specifically, I don't believe in God. And evolution is pretty much a proven fact, or at least a very much accepted and recognized theory according to rather extensive scientific evidence.
IMHO, the right of the law abiding citizen to keep and bare arms is derived from the fact that those arms exist, are legal, and, most importantly, are possessed by those who would seek to do the law-abiding harm. It is immoral to deprive the law-abiding of the very best defensive tools that the lawless plan to use against them, unless you can otherwise guarantee to protect those individuals. Which you cannot.
But it ultimately doesn't mater where those rights come from. You and your government shall not infringe those rights as stated in our 2A. If we want to democratically come together and change the 2A then take a vote. I don't believe that will happen.
Or be satisfied with the many, many current gun control regulations we already have on file. Make the FBI and other law enforcement agencies do a better job of keeping the criminal database accurate. End the war on drugs. Start making mental health more of a priority. Stop scapegoating the law-abiding by blaming them for the criminal actions of the criminal/sick/evil folks who you have no simple plan to control. Heck, teach and love your children more so they don't resort to violence to solve their problems when there are many other more healthy options for doing so.