Galaxies throughout the last 12 Gyr of cosmic time follow a single, universal fundamental plane that relates their star-formation rates (SFRs), stellar masses (M*) and chemical abundances. Deviation from these fundamental scaling relations would imply a drastic change in the processes that regulate galaxy evolution. Observations have hinted at the possibility that this relation may be broken in the very early universe. However, until recently, chemical abundances of galaxies could be only measured reliably as far back as redshift z=3.3. With JWST, we can now characterize the SFR, M⋆, and gas-phase metallicity of galaxies during the first few hundred million years after the Big Bang, at redshifts z≈7−10. Here we show that galaxies at this epoch follow universal SFR- M⋆ main-sequence and mass-metallicity scaling relations, but their chemical abundance is a factor of three lower than expected from the fundamental plane of later galaxies. Compared to state-of-the-art simulations, these findings suggest a more rapid onset of galaxy assembly and star formation than previously anticipated, and further indicate that galaxies at this time are still intimately connected with the intergalactic medium and subject to continuous infall of pristine gas which effectively dilutes their metal abundances.