The following appears in Guns, Germs, and Steel, the Fates of Human
Societies,  by Jarred Diamond, (Norton  1998):

   " Instead of being enclosed in a poppable pod, wild wheat and barley
seed grow at the top of a stalk that spontaneously shatters, dropping the
seeds to the ground where they can germinate.  A single-gene mutation
prevents the stalks from shattering.  In the wild that mutation would be
lethal to the plant, since the seeds would remain suspended in the air,
unable to germinate and take root.  But those mutant seeds would have been
the ones waiting conveniently on the stalk to be harvested and brought home
by  humans.  When humans then planted those harvested mutant seeds, any
mutant seeds among the progeny again became available to the farmers to
harvest and sow, while normal seeds among the progeny fell to the ground
and became unavailable.  Thus, human farmers reversed the direction of
natural selection by 180 degrees:  the formerly successful gene suddenly
became lethal, and the lethal mutant became successful.  Over 10,000 years
ago, that  unconscious selection for nonshattering wheat and barley stalks
was apparently the first major human "improvement" in any plant.  That
change marked the beginning of agriculture in the Fertile Crescent."
Diamond, p. 120.