SERIES INFO: This series of blog articles will include topics (and bonus sections) I couldn't fit into my book Reintroducing Jesus: Uncovering Jesus of Nazareth in the Misinformation Age.
Where the vast majority of textual variants in ancient, hand-written New Testament manuscripts are spelling and grammar mistakes—essentially an ancient version of “typos”—evidence of New Testament scribes purposely changing manuscripts do exist, though instances are rare.
Why they would do such a thing belongs to the domain of speculation, but it seems some scribes thought they were—in a misdirected way—helping. Often it seems like the change is an attempt to smooth out a perceived difficulty in the text. But like other variants, we know of these because we can plainly identify (and correct) them by comparing them to the plethora of other ancient New Testament manuscripts available to us.
Thanks to textual criticism—the study of comparing the over 5,000 ancient New Testament manuscripts and identifying differences (called variants)—we know only two variants of any size are found in the New Testament manuscript tradition.
The first is the long ending of Mark’s gospel. Based on the evidence of the earliest and best manuscripts, the textual evidence shows that Mark’s gospel ends at 16:8, but some manuscripts include a longer ending—even different longer endings.
The second variant of any size is the story of the woman caught in adultery in John 7:53–8:11. Like the long ending of Mark, the earliest and best (as well as the majority of) manuscripts of John's gospel don’t contain this passage. The fancy, scholarly title for this passage is the pericope adulterae (“adultery passage”), but I prefer to call it the pericope wandering, because not only does it awkwardly interrupt the flow of John’s narrative, but it wanders. It appears in different places in manuscripts of John’s gospel and even makes a surprise appearance in the Gospel of Luke!
We can only speculate how these passages that are plainly not part of the originals slipped into the manuscript tradition.
Mark’s gospel ends abruptly. It’s easy to imagine someone thinking it needed a more concrete closing. (Some also argue that Mark originally did have a longer ending, but it was somehow lost extremely early in the manuscript's transmission.)
The pericope adulterae—where Jesus says the much-paraphrased line, “Let him without sin throw the first stone”—is a popular and loved story (and for good reason). But, sadly, according to the physical evidence, it’s not part of what John originally wrote. Maybe someone wanted to preserve this beloved story showing Jesus’ wisdom and mercy. Maybe it’s even a true story passed down by the first Christians. All we know for certain is that it wasn’t an original part of John’s gospel. (Though I’ve heard pastors preach on this passage several times, I also know of pastors who won’t preach on it because they don’t consider it sacred scripture.)
For the reasons stated above, most modern printings of the Bible will set these two passages off with brackets with a footnote about the earliest and most-reliable manuscripts not including them.
Somewhere, someone just learned this for the first time and I just bummed that someone out—likely a Bible-believing Christian. Sorry, but listen; I’d rather you hear it from me than from your hostile comparative religions professor or that “anti-theist” internet troll.
As I said, evidence of purposeful changes within the New Testament manuscript tradition is rare. With this, a “very high percentage” of variants in the four gospels and Acts affect a verse or less . In fact, 99% of variants are—as one scholar put it—“awfully boring”.
The thing is, we’ve actually become more confident in modern times compared to, say, even 100 years ago about the original wording of the New Testament because new manuscripts are still being discovered to this day. Like the earliest fragment of John’s gospel, many documents are being discovered in archeology digs in ancient garbage dumps. Apparently, ancient Egyptian dumps are the rage with all the hip archeologists. Who knew? It looks like that weird old lady who frequents yard sales and repeatedly says, “One man’s garbage is another man’s treasure” has a point.
Case in point, not long before the writing of Reintroducing Jesus, a fragment from the Gospel of Mark was found at one of these sites . There was quite a bit of excitement that this may have been from a first century manuscript, but it dates to somewhere between AD 150–250. Regardless, it’s still an exciting find because it’s the earliest fragment of Mark’s gospel we have.
For the past 100 years, the rate of discovery of ancient New Testament manuscripts has averaged one-per-year (and, by the way, none of these have led to any discoveries of significant variants) . Not only do we have a larger collection of ancient New Testament manuscripts than ever before, but thanks to modern technology these manuscripts are more accessible for study than at any other time in history.
For the record, it’s not like Mark's long endings and John’s wandering, adulterous passage were just recently discovered as imposters. The church has known about them for centuries because even ancient scribes did textual criticism.
 John 8:7. My paraphrase.
 Myths and Mistakes in New Testament Textual Criticism, Edited by Elijah Hixton and Peter J. Gurry, Chapter 7: “Myths About Copyists: The Scribes Who Copied Our Earliest Manuscripts” by Zachary J. Cole. Kindle. Loc 3106.
 Myths and Mistakes in New Testament Textual Criticism, Edited by Elijah Hixton and Peter J. Gurry, Chapter 10: “Myths About Variants: Why Most Variants Are insignificant and Why Some Can’t Be Ignored” by Peter J. Gurry. Kindle. Loc 4095.
 “Despite Disappointing Some, New Mark Manuscript Is Earliest Yet” by Elija Hixson, Christianity Today, May 30, 2018
 Myths and Mistakes in New Testament Textual Criticism, Edited by Elijah Hixton and Peter J. Gurry, Chapter 3: “Math Myths: How Many Manuscripts We Have and Why More Isn’t Always Better” by Jacob W. Peterson. Kindle. Loc 1685.