Boerlijst, M.C., Hogeweg, P., 1991. Spiral wave structures in pre-biotic evolution: hypercycles stable against parasites. Physica D 48, 17-28. [12] Bollobas B., 1995. Random Graphs. Academic Press, New York. [13] Bonne, I., Pawlowitsch, C., 2008. One-third rules with equality: second-order evolu- tionary st