'Birth of gravity' is a lead in question to an area I fully admit ahead of time I know little. What I'm wanting to ask is: At what point in the big bang model is gravity REQUIRED in order to explain our known data? Obviously, it has been around since the time of the surface of last scattering -- but was it 'needed' before hand? My simple review of the early stage models seems to make reference to densities using General Relativity like relations. So at another level the question becomes: Are these really needed? What would be different if instead it was assumed that there was no gravity at a given 'era'? I'm honestly asking for info on this. Trying to decipher the technical papers leaves one with questions about assumptions.