Such work is at the moment under way using molecular and genetic probes, but these so far have produced unsettled and somewhat contradictory results For example, in the early work on a species of jawless lamprey, the first results identified a Hox gene expressed in the mandibular arch of lamprey embryos, but this same Hox gene was not expressed in the mandibular arch of jawed vertebrates. This suggested that this Hox gene suppressed jaw development (lamprey) and its absence (gnathostomes) removed this inhibition to facilitate evolution of jaws. However, more recent work on other species of lampreys found no such Hox expression. This suggested instead that this Hox gene is not a key component of jaw evolution.