For sake of responding to the question as posed, this post will adopt the premise that the original ending of Mark's Gospel has been lost. A more extensive discussion of evidence for and against this premise (as well as a discussion of competing theories), is presented here: The Ending of the Gospel of Mark. 1
If the original ending of Mark's Gospel has been lost, there appear to be 3 possibilities regarding Mark's relation to the other Synoptic Gospels:
A. Mark came first, and the original ending was lost after at least 1 of the other Synoptics was written
B. Mark came first, and the original ending was lost before the other Synoptic Gospels were written
C. Mark did not come first
Provenance of the Gospels
This information will be of value to the discussion insofar as it indicates that the Synoptic Gospels were published in distinct and distant parts of the Roman Empire.
Matthew: Matthew's Gospel is written to an audience that is expected to have detailed cultural understanding of the Judaism of the time & place where Jesus lived. This restricts the geographic origin of Matthew to a relatively narrow part of the Eastern Mediterranean, from approx. Judea in the south to Syria in the north. (see the section "What audience is assumed by the authors?" in this post)
Mark: All early sources place Mark's origin in or near Rome. There is no competing historical evidence.
Luke: All early sources place Luke's origin in the Pauline mission, and several early sources suggest it was published in Greece.
Mark came first, and the original ending was lost after at least 1 of the other Synoptics was written
If this happened, then in order to have been used as a source for Matthew and/or Luke, the Gospel of Mark had already achieved a geographically significant circulation prior to the loss of the original ending. This would require that the lost ending disappeared from multiple geographically dispersed manuscripts representing, in the language of textual criticism, multiple manuscript families.
The odds of this occurring by accident are prohibitively low. In order for this to have occurred on purpose (somebody painstakingly purged the ending from manuscripts spread across the Mediterranean) a degree of centralized control that did not exist in the early church would have been needed. By the 4th century, when the church did have greater centralized authority, the Gospel of Mark had been in circulation for ~3 centuries across an immense geography, and it would not have been possible to conduct an Orwellian edit to remove the ending of all manuscripts in existence in every language.
I will have to conclude that possibility A is false.
Mark came first, and the original ending was lost before the other Synoptic Gospels were written
This case offers the more plausible scenario wherein the ending was lost very shortly after Mark was published--the Occam's Razor hypothesis being that the ending was lost on the original manuscript before any complete copy had been made. In this case, Matthew & Luke recognized a fundamental part of the story was missing from their source (Mark), and composed their post-resurrection narratives from other material available to them.
From a strictly historical viewpoint, there is no clear reason why this couldn't have happened; however, the OP asks Does this indicate that the Gospel of Mark was early enough that its recipients did not realize the significance of its record to start making copies of it before it started to wear out?
I suggest at least 4 reasons why the answer to this question is no.
- Mark is a missionary tract--it is written to present the Christian message to an audience who does not know who Jesus is. The Christian movement grew geographically so fast that one copy of the Gospel of Mark would have been woefully impractical (unless a more extensive account, such as Matthew & Luke, were already available -- but in that case Matthew and/or Luke were written before the ending was lost, and possibility B is false)
- Two opposing claims must be maintained at the same time: a) For many years the Gospel of Mark existed only in a single copy, published in Rome, and available to a very limited audience & b) the Gospel of Mark was so widely disseminated that it would be the principal source used by Gospels published across the Mediterranean.
- If the ending of Mark's Gospel was lost because the scroll was so heavily used, then why couldn't those who had so heavily loved & used the scroll rewrite the ending from memory?
- Clement of Alexandria traces the origin of the Gospel of Mark in some detail, and from his account the early recipients of the Gospel of Mark very much did recognize the importance of this material. Prominent Romans are reported to have literally begged for Mark to make a written account of the preaching they had heard (see Historia Ecclesiastica 2.15.1). Clement is one of the best positioned scholars in history to know the history of this Gospel. For those who wish to discard Clement's information or disparage his credibility, this post may be of interest.
While I don't see that a lost ending of Mark is necessarily inconsistent with Markan Priority, I do not see how it supports Markan Priority either.
Mark did not come first
In this case, the answer to the OP's inquiry would be a simple "no", and Mark, presumably familiar with Matthew and/or Luke, wrote a shorter Gospel which was later damaged. If Mark was written later than Matthew and/or Luke, it is perhaps easier to see why the truncated ending of Mark would be less devastating (and therefore less in need of urgent correction), since the audience would have already had a more complete account of Easter from the other Gospels.
Mark's Gospel is the least-quoted--by far--of the 4 Gospels among 2nd, 3rd, and 4th generation Christians, suggesting that it was less prominent and less used in the early church. This would make it easier for the ending to go missing. But such lack of prominence is much easier to explain if 1 or more Gospels preceded Mark than if Mark was the primary source for the life of the central figure of Christianity.
A Relevant Synoptic Problem Argument
Sometimes the abrupt ending of Mark is used as direct evidence for Markan Priority. (how could Mark, if he knew Matthew and/or Luke, choose to leave out almost all of the Easter account?).
I offer an extended response to this question here.
But, if the original ending of Mark's Gospel has been lost, this argument loses all force. We would no longer be able to claim that Mark left out this material. In fact, no textual comparison between the ending of Mark and the ending of Matthew/Luke could be made at all, since (on this hypothesis) we do not even have the relevant text of Mark.
The hypothesis that the original ending of Mark's Gospel has been lost undoes one popular argument for the Priority of Mark, but there are other arguments for Markan Priority and a lost ending is not inconsistent with the possibility that Mark wrote first.
The hypothesis that the original ending of Mark's Gospel has been lost is also consistent with the possibility that Mark was not the earliest Gospel written. That the church could lose such an important Easter text is, in my view, easier to explain if Mark were not the primary source, but was written after Matthew or Luke had already been published.
1 - Disclaimer - this is a link to my own work on the subject