A team of University of Colorado–Boulder and University of South Florida scientists has investigated the history of the hammerhead shark using genetic methods. By constructing a “phylogenetic” tree (using evolutionary presuppositions), the researchers have concluded, among other things, that “big hammerheads probably evolved into smaller hammerheads, and that smaller hammerheads evolved independently twice,” explained Colorado evolutionary biologist Andrew Martin.
They are all remarkably similar in design.
The scientists began by gathering DNA from eight species of hammerhead sharks around the world, then sequenced the DNA and assembled a hypothetical history of hammerhead species. Such phylogenetic trees are based on the assumption that all hammerheads descended from a common ancestor—thought to have lived around 20 million years ago—and that genetic mutation rates have been constant through all that time.
Of particular interest is the team’s investigation of hammerheads’ characteristic “cephalofoils,” the technical term for their strange hammer-like heads. In addition to providing possible hydrodynamic advantages, hammerhead cephalofoils help enable electrical sensing of prey. According to Martin, “Hammerheads appear to be able to triangulate on their prey, which is remarkable.” However, the relative size of various hammerheads’ cephalofoils varies, from the large cephalofoil-to-body ratio of the winghead shark to the small ratio of the bonnethead shark.
What’s missing, of course, is a connection to Neo-Darwinian-style, molecules-to-man evolution. Although there are many species of hammerhead shark, they are all sharks—and, in fact, they are all remarkably similar in design. Even though we agree that they probably did descend from a common ancestor (perhaps a medium-sized hammerhead shark kind created during Creation Week of Genesis 1 ), variation in size, cephalofoil-to-body ratio, and other characteristics can be explained by rearrangements and removal of genetic information. Therefore, today’s hammerhead species have less genetic information than their ancestors, the opposite transition from what Darwinian evolution requires. As for the purpose of hammerheads’ “remarkable” prey-sensing capabilities in a perfect world without death, see the links below.
For more information:
Remember, if you see a news story that might merit some attention, let us know about it! (Note: if the story originates from the Associated Press, Fox News, MSNBC, the New York Times, or another major national media outlet, we will most likely have already heard about it.) And thanks to all of our readers who have submitted great news tips to us.