"Authorship"--in the sense we know it today, individual intellectual effort related to the book as an economic commodity--was practically unknown before the advent of print technology. Medieval scholars were indifferent to the precise identity of the "books" they studied. In turn, they rarely signed even what was clearly their own. They were a humble service organization. Procuring texts was often a very tedious and time-consuming task. Many small texts were transmitted into volumes of miscellaneous content, very much like "jottings" in a scrapbook, and, in this transmission, authorship was often lost.
The invention of printing did away with anonymity, fostering ideas of literary fame and the habit of considering intellectual effort as private property. Mechanical multiples of the same text created a public--a reading public. The rising consumer-oriented culture became concerned with labels of authenticity and protection against theft and piracy. The idea of copyright--"the exclusive right to reproduce, publish, and sell the matter and form of a literary or artistic work"--was born.
Xerography--every man's brain-picker--heralds the times of instant publishing. Anybody can now become both author and publisher. Take any books on any subject and custon-make your own book by simply xeroxing a chapter from this one, a chapter from that one--instant steal!
As new technologies come into play, people are less and less convinced of the importance of self-expression. Teamwork succeeds private effort.