A unified description of all interactions could be based on a higher-dimensional theory involving only spinor fields. The metric arises as a composite object and the gravitational field equations contain torsion-corrections as compared to Einstein gravity. Lorentz symmetry in spinor space is only global, implying new goldstone-boson-like gravitational particles beyond the graviton. However, the Schwarzschild and Friedman solutions are unaffected at one loop order. Our generalized gravity seems compatible with all present observations.

6 pages, LaTeX, v3: extended discussion and new references