My personal library has close to a thousand volumes. No, it isn’t much and it used to be a bit bigger but it gets the job done. Let’s say I pick a random book of the shelf like The Revenant. The cover has a bear attacking a man and has both the title of the book as well as the book’s author on it. If I open the book the first page has a short blurb about the author and other books he has written. On the backside of that page is a list of other books by the author. Opposite that is a title page featuring the name of the book and its author. We then find the copyright page which features the name of the book, its author, and the publisher. If I close the book and look at its spine I see again the book’s title and its author. Not once but six times I will have seen that the author of The Revenant is Michael Punke. There is no question to me who wrote it and I would need a very good reason to deny that Punke is the author of The Revenant. 
Now let’s take one of the four canonical Gospels that appear in the New Testament like the Gospel of Mark. Apart from the title “The Gospel According to Mark” that appears before the actual text of the Gospel itself, where do we find Mark’s name? In sixteen chapters and eleven thousand words, we don’t find Mark’s name mentioned one time. There is absolutely nothing in the Gospel of Mark that makes us think that someone named Mark wrote it. And this is true not only of the Gospel of Mark but also the Gospel of Matthew and, to a certain degree, the Gospels of Luke and John.
The Traditional View
So if there is no internal evidence for Markan authorship,  why do so many believe that Mark wrote it? By-and-large it has to do with the second century bishop Papias. Papias wrote Λογίων Κυριακῶν Ἐξήγησις, An Exposition of the Sayings of the Lord. Unfortunately, this work is no longer extant and it is only partially preserved for us in the writings of another second century bishop named Irenaeus and the fourth century bishop and historian Eusebius. It is in Eusebius’ Church History that we read Papias’ words regarding the Gospel of Mark.
This also the presbyter said: Mark, having become the interpreter of Peter, wrote down accurately, though not in order, whatsoever he remembered of the things said or done by Christ. For he neither heard the Lord nor followed him, but afterward, as I said, he followed Peter, who adapted his teaching to the needs of his hearers, but with no intention of giving a connected account of the Lord’s discourses, so that Mark committed no error while he thus wrote some things as he remembered them. For he was careful of one thing, not to omit any of the things which he had heard, and not to state any of them falsely. 
Papias is claiming a number of things: that he received this information from “the presbyter,” a likely reference to the apostle John; that Mark received the material for his Gospel from the apostle Peter himself; that Mark was not an eyewitness to the ministry of Jesus; that the Gospel was written such that it was “not in order” but everything was written down accurately. It is upon this basis that the Gospel of Mark has been attributed to Mark for the last nineteen hundred years. Is it enough?
Let’s begin with the most obvious question: Mark who? If we say that the Gospel of Mark was written by Mark, we need to figure out who this Mark character is.
In the book of Acts we read of a “John whose other name was Mark” (Acts 12:12). John Mark becomes a companion of Paul and Barnabas (Acts 12:25). Following a trip to Cyprus (Acts 13:4-12), Paul and Barnabas decided to travel to Pamphylia. John Mark, however, does not continue with them and instead returns to Jerusalem (Acts 13:13). The three are reunited at the Jerusalem Council (Acts 15). Following this important meeting, Paul and Barnabas decide to “visit the believers in every city where [they] proclaimed the word of the Lord” (Acts 15:36). Barnabas wants to bring John Mark with them (Acts 15:37) but Paul decides that he shouldn’t because he “had deserted them in Pamphylia and had not accompanied them in the work” (Acts 15:38). This causes a rift between Paul and Barnabas and the two never work together again. Barnabas takes Paul and travels to Cyprus while Paul takes Silas and travels to Syria and Cilicia (Acts 15:39-41).  Since the rest of the book of Acts focuses in on Paul and his activities, we don’t learn anymore of the work of Barnabas and John Mark.
The Jerusalem Council happened around 50 CE and all of Paul’s letters were penned after that meeting. Barnabas is mentioned by Paul in the epistle to the Galatians (2:1, 2:9, 2:13), the first epistle to the Corinthians (9:6), and in the epistle to the Colossians (4:10).  An individual named Mark is mentioned in only Colossians (4:10), 2 Timothy (4:11), and Philemon (1:24). If this is the same Mark as that of the book of Acts, then at some point he rejoined Paul on his journeys. This is the view of various commentators. 
Another individual named Mark is mentioned in 1 Peter 5:13 where he is referred to as Peter’s “son.” Though the Gospels make it clear that Peter was married (see Mark 1:30) and the apostle Paul states that Peter had a wife (1 Corinthians 9:5), we don’t know if Peter had any children. It seems unlikely, then, that this Mark is the literal son of Peter. Unfortunately, the connection between the John Mark that traveled with Barnabas and this Mark is also quite tenuous. Though in Acts we do read that the disciples were gathered in the home of Mark’s mother when Peter, an escaped convict, happened upon them (see Acts 12), that is the only connection between Peter and Mark we see in the book of Acts. Throughout the New Testament, the only whiff of a connection between the two is here in 1 Peter. And since 1 Peter was written well after Peter’s death, this connection holds little stock.  Furthermore, if Mark had been traveling with Barnabas and then at some point rejoined Paul, when did he join Peter? Philemon was written by Paul while he was under house arrest in the mid 50s CE. Did he leave Paul to go to Peter? Did this happen before or after Paul’s death? These are questions for which the New Testament offers us no answers.
We must also ask the question as to who exactly Papias meant when he named Mark as Peter’s interpreter. It is clear from the context in which Eusebius quotes Papias that he means the Mark of the book of Acts but is that what Papias meant? Since Papias’ Expositions of the Sayings of the Lord is no longer extant, we cannot be certain. And it may be that the book of Mark that Papias spoke of was not the Gospel we have today.
Problems with Papias
One of the clues that Papias may not be speaking about the Gospel of Mark we have today actually has to do with what he says (and doesn’t say) about the Gospel of Matthew. In Eusebius we read Papias’ words:
So then Matthew wrote the oracles in the Hebrew language, and every one interpreted them as he was able. 
While there is some debate as to what Papias meant by this , generally it is thought he was referring to the Gospel of Matthew as we have it. But therein lies the problem: we have no early manuscripts of Matthew’s Gospel in Hebrew or, as some have thought Papias meant, Aramaic. While undoubtedly Jesus spoke Aramaic, all of our sources are in Greek. So far, with all the evidence at hand, Papias is either wrong about our Gospel of Matthew or he had something else in mind.
The real issue is what Papias doesn’t say about the Gospel of Matthew. The majority of biblical scholars accept the notion that the first Gospel to be written was Mark’s. They also tend to think that both Matthew and Luke used Mark’s Gospel as one of the sources for their own. While we will look at Markan priority at a later time, it suffices to say that when we look at Matthew and Luke and compare them to Mark we can see that they generally follow Mark’s order of events. But if Papias was right – that Mark wrote down what Peter said in his narrative and it was “not in order” – then couldn’t the same be said about Matthew’s Gospel since it generally follows Mark’s? Yet Papias makes no statement about Matthew’s order at all.
There is yet another issue with Papias’ words about both the origin of Mark’s Gospel and Matthew’s: Papias doesn’t offer us a sample text that shows he is thinking of our Mark and Matthew. Bart Ehrman writes that
it is important to stress that in none of the surviving quotations of Papias does he actually quote either Matthew or Mark. That is to say, he does not give a teaching of Jesus, or a summary of something he did, and then indicate that he found it in one of these Gospels. That is unfortunate, because it means we have no way of knowing for certain that when he refers to a Gospel written by Mark he has in mind the Gospel we today call the Gospel of Mark. 
Remember, we don’t even have Papias’ original writings and so we don’t know if Eusebius was presenting Papias in the context of our Mark and Matthew.
So what do we do with Papias? Well, we can speculate that Papias was speaking of our Mark and Matthew, a speculation that is not conducive with the available evidence. Or we can speculate that Papias was speaking about something other than our Mark and Matthew, a speculation that is a bit more reasonable than that he was speaking of our versions. Or we can simply say Papias was flat-out wrong. I opt for the third possibility.
So Who Wrote the Gospel of Mark?
If we cannot trust Papias and we cannot go off of any internal evidence to establish authorship, what can we say about the Gospel of Mark’s author? Simply put, the answer is that we don’t know. There is nothing in the book to indicate who the author is and our traditions about the book are not all that reliable. In the absence of good evidence, saying “I don’t know” seems fitting.
But does that matter? For those concerned with canonicity it might. One of the driving forces behind connecting the Gospel of Mark with Mark is the connection to Peter via Papias. After all, Peter was an eyewitness to Jesus’ life and ministry. If Mark wrote down what Peter communicated, we would have an immediate contemporary account of the life of Jesus, albeit second-hand. And it would have apostolic authority standing behind it!
But none of the Gospels are from eyewitnesses directly or indirectly and that’s okay. That doesn’t affect our exegesis of it in the slightest. Regardless of who wrote it, it stands as a biography of Jesus from which we can learn how some of his earliest followers saw him. We can parse the words, observe the context, and offer an exposition that can be enlightening and interesting without having it connected to Mark or Peter or whoever.
It adds nothing to the Gospel.
 Not only can I see on the book that Punke is the author but I can access the Internet and search a Wikipedia page on him, watch YouTube videos featuring him, and more. The evidence that Punke authored The Revenant is overwhelming.
 D.A. Carson and Douglas J. Moo write, “But the important point is that nothing in the second gospel stands in the way of accepting the earliest tradition that identifies John Mark as its author. Our decision, then, will rest almost entirely on external evidence, and especially on the tradition handed down through Papias and Eusebius from the unnamed presbyter.” (An Introduction to the New Testament, second edition [Grand Rapids, MI: Zondervan, 2005], 175.)
 Eusebius, Church History, 3.39.15. In Phillip Schaff, editor, Nicene and Post-Nicene Fathers, series II, vol. 1 (Grand Rapids MI: Christian Classics Ethereal Library, n.d.), 379. Available at https://www.ccel.org/ccel/schaff/npnf201.pdf
 In his letter to the Galatians, likely written sometime in the 50s CE, Paul possibly offers a different explanation for his split with Barnabas. In Galatians 2 we read about Paul and Barnabas’ trip to Jerusalem for the Council mentioned in Acts 15. Whereas in Acts 15 we get the sense that Paul and Barnabas had already split up, here in Galatians 2 we see things a bit differently.
At some point Peter (i.e. Cephas) arrives in Antioch and there Paul confronts him. The issue at hand was that Peter would sit and eat with the Gentiles but when “certain people came from James” Peter withdrew from the Gentiles “for fear of the circumcision faction” (2:12). Peter’s hypocrisy evidently was contagious and Paul says that “even Barnabas was led astray by their hypocrisy” (2:13) Paul believed that Peter, Barnabas, and the rest “were not acting consistently with the truth of the gospel” and so he confronts Peter in front of them all saying, “If you, though a Jew, live like a Gentile and not like a Jew, how can you compel the Gentiles to live like Jews?” (2:14)
Barnabas isn’t mentioned again after this and it seems that the two never worked together again. But the fight does not appear to be over Mark but over the hypocrisy of Peter and Barnabas regarding table fellowship.
 The letter to the Colossians is an example of pseudo-Pauline literature. In all likelihood, Paul never wrote it. This is true of other so-called Pauline letters like Ephesians, 2 Thessalonians, 1 and 2 Timothy, and Titus.
 See Peter T. O’Brien, Colossians, Philemon, WBC, vol. 44 (Nashville, TN: Thomas Nelson Publishers, 1982), 307-308, and Scot McKnight, The Letter to Philemon, NICNT (Grand Rapids, MI: William B. Eerdmans Publishing Company, 2017), 112.
 Both of the epistles of Peter were not written by the apostle Peter and can be dated to after his death in Rome. See Claudio Moreschini and Enrico Norelli, Early Christian Greek and Latin Literature: A Literary History, vol. 1 (Peabody, MA: Hendrickson Publishers, 2005), 118. For a defense of Petrine authorship, see Carson and Moo, 641-646.
 Eusebius, 3.39.16. In Schaff, 380.
 For a discussion of Papias’ testimony regarding Matthew’s Gospel, see Donald A. Hagner, Matthew 1-13, WBC, vol. 33a (Nashville, TN: Thomas Nelson, 1993), xliii-xlvi.
 Bart D. Ehrman, Jesus Before the Gospels: How the Earliest Christians Remembered, Changed, and Invented Their Stories of the Savior (New York, NY: HarperOne, 2016), 114.
Featured image: By Phillip Vere – http://wfurl.com/a6ea272 (.pdf) “An illustrated commentary on the Gospel of Mark”. By Phillip Medhurst. .pdf file, FAL, https://commons.wikimedia.org/w/index.php?curid=34093282