My understanding is that a strong majority of scholars (including conservative scholars) take the position that the long ending of Mark was not in the original and was not written by the same author as the rest of the text, but nonetheless was added very early on (probably in the early 2nd century). However, the evidence is not as overwhelming as... See more

The longer ending (3), though current in a variety of witnesses, some of them ancient, must also be judged by internal evidence to be secondary. (a) The vocabulary and style of verses 9-20 are non-Markan. (e.g. απιστεω, βλαπτω, βεβαιοω, επακολουθεω, θεαομαι, μετα ταυτα, πορευομαι, συνεργεω, υστερον are found nowhere else in Mark; and θανασιμον and... See more