“Deeper phylogenetic relationships that are notoriously difficult to reconstruct with conventional sequence comparison methods are being resolved with miRNAs. The reason is that normal gene sequences continue to evolve after a lineage split, and, thus, the phylogenetic signal can erode by later evolution. In contrast, miRNAs stay put and, this, are like molecular fossils identifying related lineages. The only drawback is that miRNA inventories are expensive to determine and some of the data is based on the lack of certain miRNAs in certain species, which can always be a detection artifact.”