An upper bound to the supernova relic neutrino background from all past typ
e II supernovae is obtained using observations of the universal metal enric
hment history. We show that an unambiguous detection of these relic neutrin
os by the SuperKamiokande detector is unlikely. We also analyze the event r
ate in the Sudbury Neutrino Observatory (where coincident neutrons from <(n
u)over bar>D-e-->nne(+) might enhance background rejection), and arrive at
the same conclusion. If the relic neutrino flux should be observed to excee
d our upper bound and if the observations of the metal enrichment history (
for z<1) are not in considerable error, then either the type II supernova r
ate does not track the metal enrichment history or some mechanism may be re
sponsible for transforming <(nu)over bar>(mu,tau)--><(nu)over bar>(e).