From “Study of Skates and Sharks Questions Assumptions About ‘Essential’ Genes” (ScienceDaily, Dec. 15, 2011), we learn:
Biologists have long assumed that all animals with jaws and spinal columns possess nearly identical genes that regulate critical aspects of their embryological development. But a paper in the December 16 issue of Science by Benjamin King of the Mount Desert Island Biological Laboratory (MDIBL) and three of his colleagues shows that a class of fishes that includes skates and sharks lack genes that were formerly thought to be essential for their development.
King says his work shows the importance of studying all kinds of organisms, including elasmobranchs [some sharks and skates], to understand evolution. “A goal of the field of evolutionary developmental biology is to learn how developmental processes evolved by comparing many organisms with one another,” says King. “Our work illustrates the value of studying elasmobranch fishes such as skates and sharks to gain new insights. If elasmobranchs do not need HoxC genes to develop properly, we must consider the possibility that there is more flexibility in the role of the various Hox clusters than we previously thought.”
Actually, this finding shows that there is indeed more flexibility. We must consider accepting the evidence, along with what it may imply about the history of life.