1957
While Meselson and Stahl were working at the California Institute of Technology they came up with the idea that DNA replication was actually simple! *IMAGINE! THAT!*
By using bacterica they bred the bacterica in different enviornments, but using only strands from a parent bacterica. Their results showed that the generations of bacterica strands that they bred both contained traces of the parent strand. In the third generation they found strands from both the parental and the second generation!
So they not only hypothisized about DNA making a template for replication of itself they proved it.
Stahl and Meselson