I understand early versions of Unix were licenced from AT&T to Universities and ran on PDP computers. I read in Tanenbaum's book (operating systems) that the first versions of Unix were only a couple of thousands LOC. It is not detailed which functions came when. For example: When was the first version of Unix that could do pipelining with the shell?
Did the first versions even have a shell or was the interface to Unix just C and assembly?
As noted by @muru, that's fully covered in Wikipedia's page about "Pipeline (Unix)":
History
The pipeline concept was invented by Douglas McIlroy and first described in the man pages of Version 3 Unix. McIlroy noticed that much of the time command shells passed the output file from one program as input to another. The concept of pipelines was championed by Douglas McIlroy at Unix's ancestral home of Bell Labs, during the development of Unix, shaping its toolbox philosophy.
His ideas were implemented in 1973 when ("in one feverish night", wrote McIlroy) Ken Thompson added the
pipe()system call and pipes to the shell and several utilities in Version 3 Unix. "The next day", McIlroy continued, "saw an unforgettable orgy of one-liners as everybody joined in the excitement of plumbing." McIlroy also credits Thompson with the|notation, which greatly simplified the description of pipe syntax in Version 4.Although developed independently, Unix pipes are related to, and were preceded by, the 'communication files' developed by Ken Lochner in the 1960s for the Dartmouth Time Sharing System.
See that wikipedia page for additional info and references.
