I&#x27;ll have a go. Disclaimer: I&#x27;m not a biologist; corrections welcome.<p>Consider a growing multicellular organism. It grows by a process of cell division. Each division turns one cell into two adjacent cells. The structure it ends up with will depend on the orientation of those dividing cells (you&#x27;ll tend to get growth &quot;along the axis of division&quot;, so to speak).<p>A wide variety of multicellular organisms have a mechanism that orients cells according to features on the outside of neighbouring cells. (It &quot;mediates spindle orientation in diverse animal taxa by linking microtubule motor proteins to a marker protein on the cell cortex localized by external cues&quot;, as the abstract puts it. The &quot;mitotic spindle&quot; is a structure involved in cell division, also called mitosis. It&#x27;s mostly made out of long thin things called microtubules, and its job is to separate the chromosomes for the two new cells, which it does using &quot;motor proteins&quot;. The cell cortex is the inner surface of the boundary of the cell.)<p>One part of this process is the way in which a protein involved in the mitotic spindle attaches itself to that thing on the cell cortex. The relevant bit of that protein is called the &quot;guanylate kinase protein interaction domain&quot; or GK_PID for short. A protein interaction domain is a bit of protein that interacts with other things; multiple different proteins can contain instances of the same interaction domain, just as multiple different programs can contain (say) the same code for computing SHA-256 checksums.<p>The paper reports evidence that a single mutation enabled the GK_PID to attach itself to the marker on the cell cortex. (&quot;The complex was assembled through a series of molecular exploitation events, one of which – the evolution of GK_PID’s capacity to bind the cortical marker protein – can be recapitulated by reintroducing a single historical substitution into the reconstructed ancestral GK_PID.&quot;<p>So. This doesn&#x27;t say that multicellularity was enabled by a single mutation. It says that one small but important part of a process that&#x27;s necessary for complex multicellular organisms was enabled by a single mutation. Still pretty cool, but the journalistic science-&gt;hype conversion machine is clearly operating as usual here.