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The formation of galaxies by gradual hierarchical co-assembly of baryons andcold dark matter halos is a fundamental paradigm underpinning modernastrophysics. A key test of this paradigm is via the observations of massivegalaxies at early times as the evolution of the masses and abundances of darkmatter halos is straight forward to simulate and massive halos should containthe universal cosmic baryon fraction at high redshift. Extremely massivequiescent galaxies > $10^{11}$ M$_\odot$ have now been observed as early as 1-2billions years after the Big Bang producing tension with theoretical models anddriving significant revisions. Typical spectroscopic ages of these objects are300-500 Myr. Here we report on the spectroscopic observations with the JamesWebb Space Telescope of one of these objects that is quite different from therest; selected by it having much redder colours. We see spectral featurestypical of much older stellar populations and detailed modeling shows that theyformed at least 1.5 billion years earlier in time $z \gtrsim 11$ in a rapidstar formation event. Dark matter halos massive enough to host these ancestorsought not to have assembled at this time. This observation may point to asignificant gap in our understanding of early stellar populations, galaxyformation and/or the nature of dark matter.

An extraordinarily massive galaxy that formed its stars at $z \gtrsim 11$