  Reaction-diffusion equations based on a polymerization model are solved to
simulate the spreading of hypothetic left and right handed life forms on the
Earth's surface. The equations exhibit front-like behavior as is familiar from
the theory of the spreading of epidemics. It is shown that the relevant time
scale for achieving global homochirality is not, however, the time scale of
front propagation, but the much longer global diffusion time. The process can
be sped up by turbulence and large scale flows. It is speculated that, if the
deep layers of the early ocean were sufficiently quiescent, there may have been
the possibility of competing early life forms with opposite handedness.
