Is symmetry conservation an unessential feature of allosteric theory?

The role of symmetry in allosteric theory is historically and philosophically revisited. The (at least approximate) symmetry of the hemoglobin binding curves led investigators to postulate a similar symmetry or equivalence in the binding sites, which meant a symmetrical arrangement of the hemes and of the whole molecule. Later Monod introduced the concept of symmetry conservation to describe allosteric behaviour. It is shown that this postulate does not really belong to the framework of allosteric theory as it was developed in thermodynamical terms. Symmetry, however, still plays a role at levels in the underlying mathematical theory of binding and linkage in biological macromolecules.