There's a new controversial theory out now about where the synoptic gospels came from. It was once commonly accepted that Matthew was the first gospel written, but that view is largely out of favor, despite some vocal proponents. Most people believe Mark to be the earliest, and most people think Matthew and Luke used Mark and a hypothetical collection of sayings of Jesus now popularly called Q. Well, a new theory has appeared on the scene to rival these contenders: the Two-Sauce Theory!
Hat tip: NT Gateway