The John Rylands papyrus is the start of evidence. It is dated by scholars to the first quarter of the second century, 125 AD. It is an incredible find. You have to understand the weight this gives to first century authorship of the NT. Consider Ceasar's Commentarii de Bello Gallico, the oldest copy of this work is from the 10th century.
The Rylands papyrus not only gives unparralled weight to 1st century authorship, it also clearly shows how unmolested our copies are today. When the Rylands papyrus was found did anyone say, Oh we have to go back and change the book of John? No because this is what was found:
Gospel of John 18:31-33
ΟΙ ΙΟΥΔΑΙΟΙ ΗΜΙΝ ΟΥΚ ΕΞΕΣΤΙΝ ΑΠΟΚΤΕΙΝΑΙ
OYΔΕΝΑ ΙΝΑ Ο ΛΟΓΟΣ ΤΟΥ ΙΗΣΟΥ ΠΛΗΡΩΘΗ ΟΝ ΕΙ-
ΠΕΝ ΣHΜΑΙΝΩΝ ΠΟΙΩ ΘΑΝΑΤΩ ΗΜΕΛΛΕΝ ΑΠΟ-
ΘΝHΣΚΕΙΝ ΕΙΣΗΛΘΕΝ ΟΥΝ ΠΑΛΙΝ ΕΙΣ ΤΟ ΠΡΑΙΤΩ-
ΡΙΟΝ Ο ΠIΛΑΤΟΣ ΚΑΙ ΕΦΩΝΗΣΕΝ ΤΟΝ ΙΗΣΟΥΝ
ΚΑΙ ΕΙΠΕΝ ΑΥΤΩ ΣΥ ΕΙ O ΒΑΣΙΛΕΥΣ ΤΩΝ ΙΟΥ-
ΔAΙΩN the Jews, "For us it is not permitted to kill
anyone," so that the word of Jesus might be fulfilled, which he sp-
oke signifying what kind of death he was going to
die. Entered therefore again into the Praeto-
rium Pilate and summoned Jesus
and said to him, "Thou art king of the
Jews?"
Gospel of John 18:37-38
ΒΑΣΙΛΕΥΣ ΕΙΜΙ ΕΓΩ ΕΙΣ TOΥΤΟ ΓΕΓΕΝΝΗΜΑΙ
ΚΑΙ (ΕΙΣ ΤΟΥΤΟ) ΕΛΗΛΥΘΑ ΕΙΣ ΤΟΝ ΚΟΣΜΟΝ ΙΝΑ ΜΑΡΤY-ΡΗΣΩ ΤΗ ΑΛΗΘΕΙΑ ΠΑΣ Ο ΩΝ EΚ ΤΗΣ ΑΛΗΘΕI-
ΑΣ ΑΚΟΥΕΙ ΜΟΥ ΤΗΣ ΦΩΝΗΣ ΛΕΓΕΙ ΑΥΤΩ
Ο ΠΙΛΑΤΟΣ ΤΙ ΕΣΤΙΝ ΑΛΗΘΕΙΑ ΚAΙ ΤΟΥΤO
ΕΙΠΩΝ ΠΑΛΙΝ ΕΞΗΛΘΕΝ ΠΡΟΣ ΤΟΥΣ ΙΟΥ-
ΔΑΙΟΥΣ ΚΑΙ ΛΕΓΕΙ ΑΥΤΟΙΣ ΕΓΩ ΟΥΔEΜΙΑΝ
ΕΥΡΙΣΚΩ ΕΝ ΑΥΤΩ ΑΙΤΙΑΝ
a King I am. For this I have been born
fault in him."
and (for this) I have come into the world so that I would
testify to the truth. Everyone who is of the truth
hears of me my voice." Said to him
Pilate, "What is truth?" and this
having said, again he went out unto the Jews
and said to them, "I find not one
You can listen to morons endlessly try to discredit the Bible, but for a moment, consider the text on this fragment and look at the words in a modern copy of the Bible. Marvel at the transmission of these words for 2000 years. It makes people shut up.
If you would suggest the Bible has been altered, on what grounds should I consider the Nag Hammurabi or Dead Sea scrolls?