A new study combining genomic analyses and fossil evidence sheds light on the century-old “Palaeoptera Problem,” a longstanding debate over the evolutionary relationships among major groups of winged insects. The findings, published in PNAS on October 13, support the hypothesis that mayflies (Ephemeroptera) and dragonflies and damselflies (Odonata) form a single evolutionary group, Palaeoptera, which is the sister group of Neoptera, the lineage comprising insects capable of folding their wings over their bodies.