Keith Michaels schreef
But this has nothing to do with reality; if
you start with a random distribution over a large area the tendency of
one individual to move in one direction is compensated by other
individuals which backfill from nearby areas, assuming new individuals
of both orientations are being born randomly in all areas.

+ + +
It seems to me that assuming random distribution is assuming that the entire
world is flooded by a sea at a uniform depth, with water at a uniform (or at
least comparable) temperature, etc. Would certainly be the end of botany as
we know it!
PvR