  Gravitation violates baryon number $B$: A star has a huge amount of it, while
a black hole forming from the star has none. Consider primordial black holes
before the hadronic annihiliation in the early universe, encountering and
absorbing baryons and antibaryons: Each such absorption changes $B$ of the
universe by one unit, up or down. But the absorption events are $uncorrelated$
$and$ $random$, hence they amount to a random walk in $B$-space, leading to the
expectation of a net $|B|$ at the end.
  While the scale of this effect is most uncertain, it must exist. We explore
some ramifications, including the change of net $|B|$ with expansion,
connection with universe topology, and possible observational signatures.
