Time Loop In End Of Eternity

According to Senior Computer Twissell, Eternity got started in the
following manner: A man named Brinsley Sheridan Cooper from the 78th
century was inducted into Eternity and was trained in mathematics by
Twissell, in Primitive History by Andrew Harlan, and in temporal
engineering by an unknown person. He was then sent back in time to the
24th century, where he tried to train Mallansohn in temporal engineering

so that he could invent a Temporal Field Generator. However, Mallansohn

died, so Cooper had to take his place and invent the generator himself.
After convincing others that the generator was for real, he worked with
California Institute of Technology to duplicate the generator, but
didn't
dare give them information from the future, so couldn't teach them the
mathematics needed to create Eternity. Eventually, Cooper realized that

he WAS Mallansohn, and wrote a memoir that he left in a tube of Time
stasis. In the 27th century, the tube was opened by the first Computer
and the memoir read. Eventually, Twissell was given the memoir and put
in
charge of the project to send Cooper back in time to invent the Temporal

Field Generator. The memoir, of course, gave Twissell much guidance in
how to send Cooper back in time.

How did this time loop ever get started?