When were the Gospels written? A simple question with a complicated answer. Perhaps the best place to start is with the physical evidence. Some have postulated that fragment 7Q5 of the Dead Sea scrolls (68 AD at the latest) is a fragment of Mark 6:52-53, although the papyrus is so small and of such poor quality, we can't even be sure what the individual letters are, much less what words they spell, so saying that it's from Mark is purely wishful thinking.
The Rylands Papyrus (P52), supposedly containing John 18:31-33 and 37-38, has been dated to around 125 - 150 AD. However, this dating is uncertain since it is based on handwriting analysis. Carbon dating isn't used since the manuscript is so small sacrificing any part of it for carbon dating would ruin it. Therefore, the Rylands Papyrus could easily be either earlier or later than 125 - 150 AD. Even if the date is correct, we aren't even completely sure the text really is from the Gospel of John since we only have five complete words and nine partial words on one side and six complete words and seven partial words on the other. This fragment could just as easily belong to the Gospel of Nicodemus or another text entirely.
Leaving aside fragments which may or may not be from the gospels, the earliest genuine Gospel fragments of Matthew, Luke, and John date to around 200 AD which is about the same time we start seeing depictions of Jesus in artwork. Surprisingly, the oldest genuine copy of Mark now extant is the highly fragmentary Chester Beatty papyrus (P45) written around 250 AD. We know, however, that Mark had to have been written before this date since both Matthew and Luke are based on Mark.
The oldest surviving New Testament is the Codex Vaticanus written around 300 AD, although it's worth pointing out it contained a different canon than our present day Bible. Interestingly, the King James Bible originally included the Apocrypha, so our current canon is a more recent development than many people realize.
In addition to the Codex Vaticanus, there are other versions of the Bible which include different texts, as well as different versions of the Gospels. For example, one of the earliest versions of Mark ends with the death of Jesus, while later versions tack on a resurrection story. So even by the late date of 300 AD, the Gospels had not yet evolved into their final form.
In 324 AD, Emperor Constantine assembled the Council of Nicaea to unify the different versions of Christianity that had thrived in previous centuries. As part of this unification, a single version of scripture, as well as a single version of history, had to be decided upon. Eusebius Pamphilus of Caesarea rewrote his History of the Church at least five times to conform to the changing doctrine of the time.
"How far it may be proper to use fictions as a medicine for the benefit of those who require to be deceived"
-Eusebius Pamphilus of Caesarea, The title of Book 12, Chapter 31 of Praeparatio Evangelica (circa 324 AD)
Eusebius obviously had no problem with rewriting history. He tells us in Martyrs of Palestine that he intends to only list the inspiring events and leave out everything that makes the early church leaders look bad. He quotes from documents that no one before or since him had access to such as a passage from Quadratus of Athens that claims people raised from the dead by Jesus were still alive during his time, and a passage from Phlegon of Tralles which states that the day turned to night and an earthquake happened when Jesus was crucified.
Eusebius is thought to be the interpolater who inserted the reference to Jesus (known as the Testimonium Flavianum) into the writings of the historian Flavius Josephus. This obvious insertion not only breaks up the flow of the passage and was an unlikely statement for a Jew to make, but it also doesn't match Josephus' writing style, although it does match Eusebius'. Also, this passage isn't mentioned by any Christians before Eusebius.
So, keeping in mind that the historical record when it comes to early Christianity is unreliable, when are the Gospels first mentioned? The Epistle of Barnabas, written around 97 AD and the letters of Ignatius of Antioch written around 110 AD have no knowledge of the Gospels. The first epistle of Clement of Rome, written around 95 AD mentions the epistles of Paul, but not the Gospels.
Writings by Thallos (55 AD), Mara bar Serapion (73 AD), Pliny the Younger (100 AD), Tacitus (116 AD), and Suetonius (120 AD) all mention Christ (or another variant of the name such as Chrestus), yet provide no historical information about him, so there's still no evidence the Gospels have been written yet.
An earlier form of the epistles of Paul were probably written by this time, although it's worth noting that the epistles as we have them today were rewritten to conform to later theology. However, with the exception of a couple of later interpolations, even the current version of the epistles contain no historical information about Christ. Indeed, Paul talks about the crucifixion of Jesus as if it had been committed by demons before the world began. It's entirely likely that the original Christians were gnostics who believed in a spiritual Christ and only started believing in a historical Christ leading up to the time of Eusebius.
Around 130 AD, Papias of Hierapolis refers to a book by Matthew compiling the sayings of Jesus, but this is not the narrative Gospel of Matthew that we're familiar with. Papias also mentions the memoir of Peter as written down by Mark, but we have no way of knowing if this is the same as the present day Gospel of Mark.
However, even this early reference is doubtful since other Christian sources from this period such as The Book of Hermas and the writings of Polycarp still don't mention the Gospels. Also, our only source for this quote from Papias is by the pious fraud Eusebius centuries later.
The Exigetica written by the gnostic Basilides around 135 AD contained references to Gospel stories. Although, as we have no proof that the Gospels were written before this time, it's more likely the Gospels borrowed these stories from gnostic traditions rather than the other way around.
In 140 AD, Aristidies of Athens refers to "the holy Gospel writing" but we can't be sure he's refering to the same texts that we think of as the Gospels today.
The first New Testament canon was compiled by the gnostic Marcion around 144 AD. It contained ten of Paul's Epistles and one Gospel which lacked references to the nativity, the Old Testament, etc. In Against Marcion 4.2, Tertullian claims Marcion's unnamed Gospel was a stripped down version of Luke. However, as there's no evidence Luke existed before this time, it's more likely that Luke is an expanded version of Marcion's Gospel.
In his first Apology written around 150 AD, Justin Martyr refers to the writings of Mark, Luke, and Matthew as memoirs, and by about 160 AD, Tatian combines the Gospels together into a book called the Diatessaron.
Non-Christians still don't know much about Jesus during this period. Lucian of Samosata (about 165 AD) just refers to Jesus as a cruficied sophist. It isn't until about 175 AD with Celsus that non-Christians start paying attention to Christianity. In about 178 AD, Celsus wrote:
Clearly the Christians have used the myths of Danae and the Melanippe, or of the Auge and the Antiope in fabricating the story of Jesus' virgin birth. ...It is clear to me that the writings of the Christians are a lie and that your fables are not well-enough constructed to conceal this monstrous fiction. I have heard that some of your interpreters are on to the inconsistencies and, pen in hand, alter the original writings, three, four and several more times over in order to be able to deny the contradictions in the face of criticism.
In Against Heresies written about 180 AD, Irenaeus claims that there should be four Gospels and labels competing texts as heresies. The reference to the Gospels in Irenaeus is largely considered to be the first solid reference to the Gospels that we have since the earlier references to the gospels are second hand accounts quoted in later writers.
However, even the reference by Irenaues could have been written later and falsely attributed to him. Psuedopigraphs, a modern writing falsely attributed to an earlier author in order to give it more authority, were extremely common, so we can't be absolutely sure that the Gospels were even written by 180 AD. However, since we do have papyrus fragments of the Gospels from around 200 AD, it's not unreasonable to assume that the reference to them in Irenaeus is genuine.
So, based on references to the Gospels from outside sources and the existing artwork and papyrus fragments, the Gospels were most likely written sometime during the second century. Earlier or later dates than this are possible, but not very likely.
Turning to the text of the Gospels themselves, we know they were definitely not eye witness accounts due to several anachronisms. For example, Pilate was a Prefect, an office which was done away with in 46 AD, yet the Gospels refer to him as a Procurator.
Another anachronism is the existence of the city of Nazareth, as well as synagogues in Galilee, which archeology tells us weren't around until after 70 AD. Pharisees also weren't in Galilee until after 70 AD. The title of Rabbi is used to refer to Jesus, yet this title didn't come into use until the second century. In Matthew 23:35, Jesus refers to the murder of Zechariah, son of Berachiah (which happened around 70 AD) as if it had happened in the past.
The Gospels explain Jewish customs to the reader and get the geography of the area wrong, indicating that they were not written for a Jewish audience, nor were they written by someone who lived in the area.
The rabid anti-Semitism of the Gospels also indicates that they were a second century creation. After all, Christians were originally Jews, and even when Christianity began to spread to the Gentiles, they still remained on good terms with the Jewish Christians until the end of the first century where we find a Jewish prayer, the Shermoneh Esrei, cursing Nazarenes and other Christians.
For he said unto him, Come out of the man, thou unclean spirit. And he asked him, What is thy name? And he answered, saying, My name is Legion: for we are many. And he besought him much that he would not send them away out of the country. Now there was there nigh unto the mountains a great herd of swine feeding. And all the devils besought him, saying, Send us into the swine, that we may enter into them. And forthwith Jesus gave them leave. And the unclean spirits went out, and entered into the swine: and the herd ran violently down a steep place into the sea, (they were about two thousand;) and were choked in the sea. (Mark 5:8-13)
Scholars have long speculated that Legion is a reference to an occupying Roman force. Perhaps the tenth legion spoken of by Josephus:
And when he had staid three days among the principal commanders, and so long feasted with them, he sent away the rest of his army to the several places where they would be every one best situated; but permitted the tenth legion to stay, as a guard at Jerusalem, and did not send them away beyond Euphrates, where they had been before. (Josephus, Wars of the Jews Book VII, Chapter 1, Paragraph 3)
William Harwood tells us more about the tenth legion in Mythology's Last Gods: "Since the fall of the city a few months earlier [about 70 AD], Jerusalem had been occupied by the Roman Tenth Legion [X Fretensis], whose emblem was a pig. Mark's reference to about two thousand pigs, the size of the occupying Legion, combined with his blatant designation of the evil beings as Legion, left no doubt in Jewish minds that the pigs in the fable represented the army of occupation."
Mark was certainly written after the Romans had conquered Jerusalem, but how far after? Most mainstream New Testament scholars think Mark was written during the First Jewish War of 66 - 73 AD due to the so-called Little Apocalypse of Mark 13. However, most mainstream New Testament scholars are Christians with an obvious agenda to prove that the Gospels are at least partially historical. We have no outside proof that Mark was written this early. In fact, the Little Apocalypse of Mark is actually a better reference to the Second Jewish War of 132-136 AD.
And Jesus answering said unto him, Seest thou these great buildings? there shall not be left one stone upon another, that shall not be thrown down. (Mark 13:2)
This is an obvious reference to the destruction of the Temple at Jerusalem in 70 AD. Because of this passage, no serious scholar claims Mark could have been written before this date. However, great buildings were also destroyed in the Second Jewish Revolt.
For false Christs and false prophets shall rise, and shall shew signs and wonders, to seduce, if it were possible, even the elect. (Mark 13:22)
There were certainly false prophets during the First Jewish Revolt as there have been all throughout Jewish history, however, the Second Jewish Revolt had a rather high profile false prophet. Simon ben Kosiba (or Bar Kochba) not only lead the Second Jewish War against Rome and was considered the Messiah by many, but he was also said to have spewed fire from his mouth, fitting the description of one who shows signs and wonders.
But take heed to yourselves: for they shall deliver you up to councils; and in the synagogues ye shall be beaten: and ye shall be brought before rulers and kings for my sake, for a testimony against them. (Mark 13:9)
The Jews first instituted a curse upon apostates in the 90s and their hatred of Jewish Christians was at its peak in the decades immediately following. We have no evidence of Jewish violence against Christians during the First Jewish War.
The abomination of desolation, spoken of by Daniel the prophet, standing where it ought not, (let him that readeth understand,) then let them that be in Judaea flee to the mountains. (Mark 13: 14)
The "abomination of desolation" Daniel mentions in Daniel 9:27 is a statue of Zeus put in the Temple of Jerusalem by Antiochus Epiphanes about 165 BC. Hadrian modeled himself on Antiochus and actually provoked the Second Jewish War by erecting not just a statue, but an entire temple to Zeus in Jerusalem. There wasn't a clear "abomination of desolation" during the First Jewish War.
The aside by Mark (let him that readeth understand) is a formula used in the Bible to indicate that the author can't directly say what he means. We see the same thing in Revelations where John refers to Rome as the "Whore of Babylon," since he, like Mark, is unable to criticize Rome openly.
And pray ye that your flight be not in the winter. (Mark 13:18)
The reference to a flight in winter only makes sense when applied to the Second Jewish War when the Roman armies partially withdrew to regroup, making escape for the Jews trapped in the city possible. This same scenario didn't happen during the First Jewish War.
And when ye shall hear of wars and rumours of wars, be ye not troubled: for such things must needs be; but the end shall not be yet. (Mark 13:7)
This indicates that the author was aware that the First Jewish War wasn't the end, that there would be more fighting to come.
Could Mark have been written during the First Jewish Revolt, then updated after the Second Jewish Revolt? It's certainly possible. However, if we also consider the evidence of papyrus fragments and references to Mark in other historical works, we don't see any evidence to suggest Mark was written at such an early date. However, since Mark's Jesus is largely based on the stories of Elijah and Elisha as found in 1 & 2 Kings, the outline could possibly have been written any time in the previous centuries.
Who wrote Mark? Mark, the assistant of Peter isn't very likely given the evidence. Some scholars have suggested the gnostic Marcion. Others think it may have been composed by Cerinthius who founded the Cerinthians in about 140 AD since they relied solely on the Gospel of Mark. Ultimately, we don't know for sure, but as to when Mark was written, all evidence points to the 130's AD when the Second Jewish Revolt occurred and the first reference to Mark is made by Papias.
If Eusebius' quote of Papias is to be believed, Papias also referred to Matthew having collected the sayings of Jesus. This obviously wasn't a narrative story, but could this be the hypothetical Q document?
Q is a hypothetical text which hasn't survived, but many scholars believe existed since when you compare Matthew and Luke side by side, Jesus will often say the same things but in different contexts. If Luke had copied these saying from Matthew or vice versa, rearranging the order of the sayings doesn't make any sense. Therefore, the sayings common to Matthew and Luke came from a different source, a sayings document similar to the Gospel of Thomas.
Q is mainly composed of sayings from Cynic and Stoic philosophy predating the Gospels by centuries, which isn't surprising given that the Gospels were originally written in Greek and show tremendous Greek influence. Not only is the word synagogue Greek, but Jesus' disciples Andrew, Philip, and Simon have Greek names. Matthew even quotes from one of Aesop's fables (Matthew 11:17). Why Papias would associate these sayings with Jesus is unknown, but once the connection was made, both Matthew and Luke thought it would be a good idea to expand Mark's Gospel by adding these sayings to it.
The fact that the Gospel of Matthew is based on the Gospel of Mark immediately places it at a later date. However, there are also other indications that Matthew is a second century creation.
First, the nativity story of Matthew 2 involving the slaughter of innocents is based on the nativity story of Moses as told by Josephus. We know Matthew used Josephus because the version found in Exodus doesn't mention a prophecy.
One of those sacred scribes, who are very sagacious in foretelling future events truly, told the king, that about this time there would a child be born to the Israelites, who, if he were reared, would bring the Egyptian dominion low, and would raise the Israelites; that he would excel all men in virtue, and obtain a glory that would be remembered through all ages. Which thing was so feared by the king, that, according to this man's opinion, he commanded that they should cast every male child, which was born to the Israelites, into the river, and destroy it. (Antiquities of the Jews - Book II, Chapter 9, Paragraph 2 written around 94 AD)
Second, Matthew quotes from the letters of Ignatius of Antioch written around 110 AD.
No one who professes faith falls into sin, nor does one who has learned to love hate. The tree is known by its fruit. (Ignatius, Letter to the Ephesians 14:2)
Either make the tree good, and his fruit good; or else make the tree corrupt, and his fruit corrupt: for the tree is known by his fruit. (Matthew 12:33)
In all circumstances be wise as a serpent, and perpetually harmless as a dove. (Ignatius, Letter to Polycarp 2:2)
Behold, I send you forth as sheep in the midst of wolves: be ye therefore wise as serpents, and harmless as doves. (Matthew 10:16)
Unless we accept the improbable scenario of a Christian trying to pass off the wisdom of Jesus as his own sayings, we're forced to conclude that Matthew is quoting from Ignatius instead of the other way around.
Third, Matthew attempts to discredit second century rumors:
Now when they were going, behold, some of the watch came into the city, and shewed unto the chief priests all the things that were done. And when they were assembled with the elders, and had taken counsel, they gave large money unto the soldiers, Saying, Say ye, His disciples came by night, and stole him away while we slept. And if this come to the governor's ears, we will persuade him, and secure you. So they took the money, and did as they were taught: and this saying is commonly reported among the Jews until this day. (Matthew 28:11-15)
The claim that Jesus' body was stolen from the tomb was first mentioned in 160 AD, therefore this attempt to refute it was probably made later. At least, it couldn't have been made much earlier.
His disciples stole him by night from the tomb, where he was laid when unfastened from the cross, and now deceive men by asserting that he has risen from the dead and ascended to heaven. (Justin Martyr, Dialogue with Trypho the Jew, Chapter CVII, written around 160 AD)
This is your carpenter's son, your harlot's son; your Sabbath-breaker, your Samaritan, your demon-possessed! This is he whom you bought from Judas. This is he who was struck with reeds and fists, dishonored with spittle, and given a draught of gall and vinegar! This is he whom his disciples have stolen secretly, that it may be said, 'He has risen', or the gardener abstracted that his lettuces might not be damaged by the crowds of visitors! (Tertullian, De Spetaculis 100.30 written about 200 AD)
Most scholars agree that the genealogy of Jesus listed in Matthew 1 included four women of questionable backgrounds who nevertheless lived lives of repute in order to dispel rumors that Jesus' real father was a Roman soldier named Panthera. If these women with questionable backgrounds nevertheless lived lives of virtue, so did Mary. However, the first mention of this claim wasn't made until 175 AD by Celsus.
The Gospel of Matthew was most likely written around 150 AD when it is first mentioned by Justin Martyr, however, both earlier and later dates are possible.
Like Matthew, Luke is also based on Mark with the addition of Q. Luke also gets the idea for his nativity story from Josephus, but instead of referring to the Slaughter of Innocents at the time of Moses, he instead refers to the census of Quirinius (sometimes transliterated as Cyrenius).
Now Cyrenius, a Roman senator, and one who had gone through other magistracies, and had passed through them till he had been consul, and one who, on other accounts, was of great dignity, came at this time into Syria, with a few others, being sent by Caesar to be a judge of that nation, and to take an account of their substance. (Josephus, Antiquities Book 18, Chapter 1, Paragraph 1)
And it came to pass in those days, that there went out a decree from Caesar Augustus that all the world should be taxed. (And this taxing was first made when Cyrenius was governor of Syria.) And all went to be taxed, every one into his own city. (Luke 2:1-3)
However, the Census of Quirinius was based on property, not head count. There would be no reason for Joseph to return his family to his ancestral homeland for this census. The Kata Oikian census taken in Egypt in 104 AD that did require temporary city dwellers to return to their regular domiciles fits the census mentioned by Luke better.
Another reference to this census, the purpose of which was taxation, is made in Acts. As many scholars have noted, Acts seems to be a continuation of Luke written by the same author.
Judas of Galilee rose up in the days of the census, and drew away many people after him. He also perished, and all who obeyed him were dispersed. (Acts 5:37)
It was that a certain Galilean, whose name was Judas, prevailed with his countrymen to revolt, and said they were cowards if they would endure to pay a tax to the Romans and would after God submit to mortal men as their lords. (Josephus, The Wars of the Jews, Book II, Chapter 8, Paragraph 1, written around 79 AD)
Josephus is the only person to associate Judas the Galilean with the Census of Quirinius besides Luke. Since Josephus provides more details than Luke, it's highly unlikely that Josephus copied from Luke, therefore, Luke had to have copied from Josephus.
Luke actually relies upon Josephus quite heavily. He is the only writer other than Josephus to use the word haireseis to refer to different sects and the Latin word sicarii to refer to Jewish rebels.
They both use the same three rebel leaders Judas the Galilean (see above), Theudas (Acts 5:36; Antiquities 20.97) and a rebel refered to only as "The Egyptian" (Acts 21:38; Wars 2.261-263, Antiquities 20.171). They both refer to the death of Agrippa I as being a punishment from God (Acts 12:21-23; Antiquities 19.343-352).
The passages where Luke connects Agrippa II with Berenice (Acts 25:13, 25:23, 26:30) and Felix with Drusilla (Acts 24:24-26) are confusing unless the reader is already familiar with Josephus' accounts (Antiquities 20.145, 20.143).
There are many other examples such as the mention of Lysanias, tetrarch of Abilene (Luke 3:1; Wars 2.215, 2.247, Antiquities 19.275), the mention of a famine during the reign of Claudius (Acts 11:28-29; Antiquities 3.320, 20:51-53, 20.101), the similarity between Josephus' description of Herod and Luke's parable of the hated king (Luke 19:12-27; Wars 1.282-285), the siege of Jerusalem being described in a similar way (Luke 19:43-44; Wars 6), and the similarity between Pilate's attack on the Galileans in Luke 13:1 and Pilate's attack on the Samaritans in Antiquities 18.85-87.
Luke admits that he's not an eye witness, but rather constructed his Gospel by referring to historical records, so it's not surprising he relied so heavily upon the works of Josephus. In fact, Luke is the only Gospel which makes an attempt at historical accuracy.
Forasmuch as many have taken in hand to set forth in order a declaration of those things which are most surely believed among us, Even as they delivered them unto us, which from the beginning were eyewitnesses, and ministers of the word; It seemed good to me also, having had perfect understanding of all things from the very first, to write unto thee in order, most excellent Theophilus. (Luke 1:1-3)
It's worth noting that the only Theophilius known to early Christianity was made Bishop of Antioch about 170 AD. If Luke is addressing his writing to this Theophilius, which is likely, his Gospels couldn't have been written before this date. However, as Theophilius literally means "friend of God", some have speculated that Luke is not addressing a particular person, but rather Christians in general. If this is the case, Luke could have been written a couple decades sooner.
Mark, Matthew, and Luke are referred to as the synoptic Gospels because they all follow the same basic outline. The reason for this, of course, is that Matthew and Luke are based on Mark. John, however, is quite different.
The writer of John had no knowledge of Semitic languages and instead uses pagan vocabulary. Jesus lacks a Jewish genealogy and is not referred to as a Jewish Messiah. In fact, John is entirely anti-Semitic, going so far as to condemn the Jews as Satanic.
This, however, doesn't help us with dating. John could either be a later writing in which the Jewish element has been stripped out, or an earlier writing written before the Jewish character was inserted. Of course, it's also possible that John was written at the same time as the synoptics by a different community drawing on similar traditions.
Most scholars would say that John was written last due to its more advanced theology and the fact that the end of the world isn't right around the corner. However, other scholars contend that John was written first.
Tradition places the date of the Gospel of John at 96 AD due to the statement of the Monarchian Prologue (written around 200 AD) that "[John] wrote this Gospel in the Province of Asia, after he had composed Revelation on the Island of Patmos." However, it's extremely unlikely that the author of the Gospel of John is the same as the author of Revelations since the two books are so completely different from each other. Also, John doesn't read like an eye witness account, so it's doubtful that Jesus' disciple, if he existed, had anything to do with writing it.
Some have found similarities between the Gospel of John and the Dead Sea Scrolls (written between about 150 BC to 70 AD), including duplicate phrases and themes particularly in the Rule of the Community scroll (1QS 3:13 - 4:14). However, since these themes and phrases occur elsewhere, it's not certain that there's a relationship between the documents at all, and even if there is, it's more likely John copied from the Dead Sea Scrolls rather than the other way around since the Dead Sea Scrolls predate the earliest copies we have of John.
Some have pointed out similarities between the Gospel of John and the writings of Justin Martyr (about 150 - 160 AD). Again, we can't be sure of who is borrowing from whom.
Some have proposed that John is a response to Valentinus' Gospel of Truth written about 160 AD, or even a Catholic rewrite of Cerinthius' Gospel written around 140 AD. Indeed, many scholars have noted that John does appear to be a gnostic gospel that was rewritten to conform to Catholic theology.
The reoccurring theme in John of the expulsion of Christians from the synagogues indicates the earliest possible date of composition to be about 100 AD. The ideas behind John, of course, go back much further.
Philo of Alexandria (who lived from about 20 BC - 50 AD) was a Jew who worshipped Greek gods. He used the concept of Logos to try to reconcile the two traditions. Since Christianity is basically just a blend of Greek and Jewish religious traditions, one might almost say that Philo was the first Christian. His conception of Logos (the Word) is most famously brought to life in the Gospel of John:
In the beginning was the Word, and the Word was with God, and the Word was God. And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth. (John 1:1,14)
John's Jesus is not portrayed as a human. He displays no emotions or sensitivity to pain. In John, there is no nativity story, Jesus simply appears. Jesus, being perfect, does not require baptism nor does Satan try to tempt him in the wilderness since one cannot tempt a God. The synoptic Jesus refuses to give signs of his authority or say who he is, while John's Jesus is constantly giving signs and speaking of his identity.
Before 200 AD, Christianity was so similar to Greek mystery cult worship that most people couldn't tell the difference. Early church leaders such as Justin and Tertullian had to defend Christianity against charges that it was the same as Dionysus or Osiris worship.
Could John have been written before the other Gospels? The gnostic idea of Jesus as God certainly predates the Christian idea of Jesus as a man. However, as John does show an awareness of the synoptics and refutes them at times, it was probably written afterwards, placing its composition at some time around 170 AD.