Mammalian evolution exhibits extraordinary acceleration in phenotypic complexity while displaying genetic conservation. Indeed, protein-coding genes are 90% identical between mice and human, and the question arises what might be the mechanisms by which phenotypic complexity increases while the number of proteins does not? An interesting possibility is that the increase in regulatory complexity, as reflected in a more sophisticated spatio-temporal regulation on gene expression, could generate more diverse combinations of proteins and a greater number of distinct phenotypes. Importantly, unlike protein coding genes, long noncoding RNAs (lncRNA) exhibit only 50% similarity between mice and human.1 Are these RNA species involved in such regulation?