We modeled the rate of binding of precursors to the replicator assemblies based on the relative binding energies between precursors and the replicator assemblies. We approximated this binding energy as the sum of the pairwise interactions energies between the constituent building blocks (E AA , E BB and E AB ). Specifically, ΣEtf is the sum of these pairwise energies for trimer t binding to hexamer fiber of average composition f, when taking the lowest possible (most negative) value for this sum.