  Cosmological measurements of both the expansion history and growth history
have matured, and the two together provide an important test of general
relativity. We consider their joint evolutionary track, showing that this has
advantages in distinguishing cosmologies relative to considering them
individually or at isolated redshifts. In particular, the joint comparison
relaxes the shape degeneracy that makes $f\sigma_8(z)$ curves difficult to
separate from the overall growth amplitude. The conjoined method further helps
visualization of which combinations of redshift ranges provide the clearest
discrimination. We examine standard dark energy cosmologies, modified gravity,
and "stuttering" growth, each showing distinct signatures.
