"It is not known when the first quills appeared, but it is known that some parts of the Dead Sea Scrolls were written with quill in 2nd century BC. St. Isidore of Seville mentions them in the 7th century in his writings, and it is believed that quills then began to spread as a popular method of writing as better than reed pens. With quills, it was easy to write on parchment and vellum. They were also used with fine brushes to illustrate manuscripts with figures, decorations, and images and become more and more popular from the 15th century on, when writing and flourished writing started to spread through the western world." Source: History of Pencils.
This is calligraphy, which is closer to drawing than actual writing.
"What does the quill pen have that the reed pen doesn’t? For starters, the quill is as light as a feather (Literally). The aerodynamics that the feather provides helps with the swiftness that occurs when you write. The quill is definitely thinner than the reed pen and therefore, easier to handle. The quill and reed pen both share the ability to store ink due to capillarity but the quill is more versatile in writing miniscule scripts and perfecting strokes. There may be a correlation between the size/appearance of the scripts during this period and the switch to the quill." Source: Dartmouth Ancient Books Lab.
Note: Feathered quill pens are apparently just a Hollywood invention.
Comment: Quill pens may seem primitive, but the writers who used them could be very productive despite the fact that the pens had to be re-inked constantly and wore out quickly. Just to take one relatively modern example, Charles Dickens used quill pens to write "well over a dozen major novels and novellas, a large number of short stories, including a number of Christmas-themed stories, a handful of plays, and several non-fiction books." (Wikipedia) He was just as productive, if not more so, than writers working with word processors today, so it's obvious that your productivity as a writer has nothing to do with the tools you use.