These manuscripts are of a special class for two reasons.They are written on papyrus and date from well before the fourth century.
Handwriting is a product of human culture and as such it is always developing.
Differences in handwriting are bound to appear within one generation.
In the sixteenth century the Greek New Testament was published for the first time in printed form.
The great Dutch philologist Desiderius Erasmus of Rotterdam had established a text from a handful of manuscripts dating from the later Middle Ages.
Then, within a fairly short period, a number of manuscripts of superior quality became available, mainly thanks to the work of the German scholar Constantin Tischendorf.
These manuscripts dated from the fourth and fifth centuries and presented a text that was at least free from the accretions of a later age.They believed that their text reflected the original as well as possible, even if it was based on manuscripts dating from at least three centuries after the New Testament was written.Gradually the new critical texts replaced Erasmus' text, which has not received much attention from serious scholars anymore.A science called textual criticism deals systematically with these mistakes to eliminate as many of them as possible.The most important tools for textual critics are the manuscripts themselves.In the 30's and 60's of the twentieth century a number of other, very important manuscripts have become available.