Markan priority is the view that Mark is the oldest Gospel and is the prototype for the other Gospels. Mark wrote first, then Matthew and Luke composed their Gospels by adding to the framework of Mark. There is significant evidence that Mark is the original Gospel:
Figure 2.3—Did the Gospel Writers Use Each Other As Sources?
While a few scholars hold to the literary independence of the Synoptics, most see at least some literary relationship between them. The following are some key reasons.
 Strauss, Mark L.. Four Portraits, One Jesus: A Survey of Jesus and the Gospels (Kindle Locations 1127-1133). Zondervan. Kindle Edition.