Open your Bibles and look at Mark 16:8-9. In your Bible there is a footnote in between verses 8 and 9. Mine says “Some of the earliest manuscripts do not include 16:9-20″. How many times have you just read right over that and not even considered it? The end of Mark has become a disputed topic and probably the most disputed section of text in the New Testament. Some think that the gospel of Mark should end at verse 8, while others like it to end with verse 20. The question debated being, did Mark actually write these verses or were they added later? We will look at the two major sides of this debate. The first side argues that the verses were not written by Mark and were added later so they should be removed from the Bible. The second side argues that these verses were inspired by God and should remain in the New Testament. This is still an ongoing debate by people much smarter than I, so we’re just going to look at the sides and then you’re on your own.
First of all you must understand that the Bible that we have today has been passed down through history, but not always in its present form. Before the invention of the printing press, Christians had to rely on hand-written manuscripts that were passed down and copied. Eventually the Bible was collected into what is the present form. Translators attempt to translate the Bible from many sources including these ancient, hand-written manuscripts, so that the Bible is as close to the original writings as possible. There are a lot of other factors that go into it, but that is the general idea.
The reason for the footnote at the end of Mark is that there are a few ancient manuscripts of the New Testament that end at verse 8. The kicker is that two of the oldest Greek manuscripts, Sinaiticus and Vaticanus, are among those that end abruptly at verse 8. This is important because if verses 9-20 were added, then it had to be done fairly early. 
There is however a large space in the Vaticanus between Mark 16:8 and the beginning of Luke (see image), which could be where the author was debating whether or not to include the extra verses. Ending Mark at verse 8 has not been the traditional accepted view throughout history, but this could be due to the fact that some of the older manuscripts supporting it were not discovered until the 1800s.
The supporters of the inclusion of verses 9-20 point out that the majority of the manuscripts include these verses. None of these manuscripts are older than the Sinaiticus and Vaticanus, which exclude 9-20. Some early church fathers quoted from these extra verses, giving support to including them. There is a possible early reference to 9-20 in Justin’s writings in 160 AD, but the earliest sure reference to these extra verses is by Irenaeus in 177 AD. What is problematic is that even more of the early church fathers did not quote verses 9-20. There are multiple church fathers, such as Clement and Origen, who never make any references to these verses. Eusebius, who lived in the late 3rd and early 4th century, stated that he believed that the verses did not appear in any accurate manuscripts.
There are also some style problems with verses 9-20, such as the introduction of Mary Magdalene again. Mary Magdalene was introduced in Mark 16:1, but for some reason she is reintroduced in Mark 16:9. 
These verses also have been used to support some more extreme doctrines such as baptism as a requirement for salvation, drinking poison for God and snake handling. The latter two may seem a little more extreme.
It does seem odd that Mark would just abruptly end his gospel in verse 8, but many have considered the fact that Mark may have been incapable of finishing his writing due to extenuating circumstances, such as death. This has led to the theory that perhaps someone close to Mark finished up where he was unable to finish. This would explain the style change and could explain the verses’ absence in some manuscripts. However it has to be considered whether or not this new writer qualifies for writing scripture. Usually the qualifications include either first-hand exposure to Christ’s teachings or direct teaching from someone who did have first-hand exposure. Mark meets these qualifications by his friendship with Peter, like Luke and his friendship with Paul. You have to wonder if the person who finished Mark’s gospel was cool enough to write the inerrant Word of God.
When contemplating the idea that these verses could possibly have been included afterwards, we need to consider the impact that these verses have on our beliefs, theology and worship practices. While Christ’s words in Mark 16:9-20 do promise some extreme signs to accompany the Apostles’ ministry, all but the poison drinking actually do occur in the books of Acts. I think it is important that we do not base major doctrine on a single scripture, especially if the scriptures are disputed like these. The majors themes and pillars of Christianity seem to be conveniently and consistently repeated throughout the New Testament. Though if you choose to “prove your salvation” by sipping down some poison, then you are on your own.
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