  Galaxies throughout the last 12 Gyr of cosmic time follow a single, universal
relation that connects their star-formation rates (SFRs), stellar masses
($M_\star$) 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, $M_\star$, and chemical
abundance 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
unique SFR-$M_\star$--main-sequence and mass-metallicity scaling relations, but
their chemical abundance is a factor of three lower than expected from the
fundamental-metallicity relation of later galaxies. These findings suggest 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.
