How much of the stuff that our genomes do is actually functional? We set out to answer this long debated question by creating a null hypothesis in yeast and human in the de Boer Lab's latest preprint: 1/ biorxiv.org/content/10.110… It's often assumed that any reproducible activity of the genome (eg histone modification, transcription) is functional; but is this really true? Without knowing what to expect by chance (e.g. in the absence of selective pressures), this is difficult to answer. 2/