The earliest Gospel was not simply a collection of Jesus lore. It thus is not a window through which to observe traditions about Jesus, nor is it a quilt of earlier written collections stitched together. Rather, it is a tapestry skillfully woven from threads most often supplied by Jewish scriptures in Greek. To be sure, some of the threads may issue from oral/aural communications, but when textualized they are nearly indistinguishable from the author's originality. The Logoi of Jesus thus is a textus, "something woven", from the Latin verb texere, "to weave". Furthermore, Mark's extensive reliance on it for Jesus's teachings, and the obsession of Matthew, Papias and Luke with these two earlier Gospels greatly reduces the content attributable to oral tradition, to say nothing of their historical reliability. What Plato was to Socrates, the author of Logoi was to Jesus.
(Dennis R. MacDonald,
From the Earliest Gospel (Q+) to the Gospel of Mark, p. 218)
The Appendix 5 is titled
Scholars Who Argued that Mark Used Q (with James R. Van Dore).
They are Legion!
Van Dore concluded that even though, when compared in isolation, none of the units that comprise the clusters unambiguously reveals evidence of Mark's retention of Q's redaction, their similar combinations in Q and Mark require a literary nexus. Furthermore, wherever one can discern the primitivity of one version over another, Q is anterior to Mark.
(
ibid., p. 280)
Now it becomes clear why,
if Q is absorbed entirely in
Mcn, then
Mcn's priority over Luke implies virtually also
Mcn's priority over Mark.