  We consider geometric flows of hypersurfaces expanding by a function of the
extrinsic curvature and we show that the homothethic sphere is the unique
solution of the flow which converges to a point at the initial time. The result
does not require assumptions on the speed other than positivity and
monotonicity and it is proved using a reflection argument. Our theorem shows
that expanding flows exhibit stronger spherical rigidity, if compared with the
classification results of ancient solutions in the contractive case.
