Do fermions and bosons produce the same gravitational field?

We examine some cosmological consequences of gravity coupling with different strength to fermions and bosons. We show that this leads to a different perturbation of the standard picture of primordial nucleosynthesis than the addition of extra neutrino types or overall scaling of the value of G. Observed abundances of deuterium and ^4He place bounds on the ratio of the bosonic gravitational constant (G₁) to the fermionic gravitational constant (G₅) of 0. 45<G₁/G₅<0. 92 at 1 and 0. 33<G₁/G₅<1. 10 at 2. A value of G₁<G₅ can reconcile the current ``tension'' between the abundances of deuterium and ^4He predicted by primordial nucleosynthesis. We comment briefly on other cosmological effects.