What if Einstein never discovered the equation?

Sivanesan Subramaniam from Malaysia asks:

      What would have happened, if Einstein never discovered the equation?

My personal point of view is that  some other scientist would arrive to the same conclusions very soon. The special theory of relativity (and consequently the famous E=mc² equation) was 'in the air'. Lorentz transformations  and Poincare` group were used by Einstein in the formulation of his special theory of relativity. His big intuition consisted in giving a right interpretation of the effect, correcting some mistakes made by his predecessors and coming to the elegant formulation of the theory.

On the contrary, his general theory of relativity, with the new equations of gravitation, which was published ten years later, brought into the 1916 scientific community a really revolutionary and absolutely original new idea.