The Lamprey Lethenteron Japonicum (IMAGE) University of Bristol Caption Vertebrates have long been perceived as more complex than their spineless relatives, but it has proven difficult to identify causal mechanisms underpinning the comparative complexity of even the most primitive living vertebrates such as the lamprey. The solution may be found in microRNAs, tiny non-coding RNA molecules that regulate the translation of messenger RNA during embryonic development. The diversity of microRNAs increased manyfold and at an unprecedented rate at the origin of vertebrates, coordinating the development of vertebrate evolutionary innovations. Credit Image courtesy of Shigeru Kuratani, RIKEN-CDB Usage Restrictions For single use only to illustrate articles about this news release. Not to be archived. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.