Sharks swim sideways according to reports in New Scientist 27 July 2016 and Nature Communications doi:10.1038/ncomms12289, 26 July 2016. Hammerhead sharks are well known for their strange head shape, but they also have unusual fins. Most sharks have longer pectoral fins than dorsal fins. They use their pectoral fins to stop themselves from sinking, while their dorsal fins facilitate quick turns and other manoeuvres.
An international group of scientists noted that hammerhead sharks have larger dorsal fins than pectoral fins, so they studied how hammerhead sharks swim by tagging sharks with accelerometer loggers, which keep track of body orientation as the shark swims, along with video recordings of the sharks. They also made a scale model of a shark and tested it in a wind tunnel to measure the forces acting on it at various orientations.
They found “Tagged wild sharks spend up to 90% of time swimming at roll angles between 50° and 75°, and hydrodynamic modelling shows that doing so reduces drag—and in turn, the cost of transport—by around 10% compared with traditional upright swimming”. They went on to comment: “Employment of such a strongly selected feature for such a unique purpose raises interesting questions about evolutionary pathways to hydrodynamic adaptations, and our perception of form and function”.
Editorial Comment: Here is a classic case of the misuse of words such as selection and adaptation to prop up the idea that evolution gave this shark its efficient form of swimming. Forgive our repetition, but something can only be “strongly selected” if it already exists. Selection cannot change an upright swimming shark into a side swimming shark. Selection is not a creative process. At best it can maintain useful features, at worst it results in death of creatures that do not have features needed to live in a particular environment.
The long dorsal fin and angled swimming are not “adaptations”. Adaptation is the inbuilt genetic ability to alter structures and functions in response to changing needs. No-one has seen a shark change its fins or swimming action from a horizontal swimming shark with shorter dorsal fin to the fins and action of the hammerhead.
In fact, the fins and swimming action are design features that only work because they were built in from the beginning by the Creator, who made the whole creature with the right fins and the nervous system control needed to swim in this unique way. So note our prediction: The questions about pathways to hydrodynamic adaptations may be interesting, but will never be answered by evolution. (Ref. fish, locomotion, biomechanics)
Evidence News vol. 16 No. 15
17 August 2016
Creation Research Australia