  We compute the tree level 4-particle bosonic scattering amplitudes in D=11
supergravity. By construction, they are part of a linearized supersymmetry-,
coordinate- and 3-form gauge-invariant. While this on-shell invariant is
nonlocal, suitable SUSY-preserving differentiations turn it into a local one
with correct dimension to provide a natural lowest (two-loop) order counterterm
candidate. Its existence shows explicitly that no symmetries protect this
ultimate supergravity from the nonrenormalizability of its lower-dimensional
counterparts.
