November 23, 2009 | David F. Coppedge

Hammerhead Sharks Have 360-degree Stereo Vision

Scientists at Florida Atlantic University have found that the strange heads of hammerhead sharks give them exceptional binocular vision.  This has long been debated.  By placing electrodes in the eyes of three hammerhead species, and comparing the visual overlap they obtain compared to other sharks, the scientists confirmed that there is a “massive 32-degree overlap” in their forward vision, providing stereoscopic acuity, even though the eyes are seemingly pointed in opposite directions.  The researchers concluded, “They have a full 360-degree view of the world.”  The story was reported by Live Science, National Geographic, BBC News, and New Scientist.
    Live Science and National Geographic did not mention evolution.  The BBC article mentioned it in passing.  Dr. Michelle Macomb, one of the researchers from Florida Atlantic University, was quoted as saying that “This study has confirmed that vision may have played a role in the evolution of one of the ocean’s most bizarre inhabitants.”  This statement, of course, offers no insight into how that might have occurred.  In the New Scientist article, by contrast, Shanta Barley started right off on a Darwinian foot, mentioning evolution in each of the first three sentences:

It’s one of evolution’s most eccentric creations: a head shaped like a hammer.  Now, a study suggests that the hammerhead shark may have evolved its oddly shaped snout to boost the animal’s vision and hunting prowess.
    For over a century, scientists have speculated why hammerheads evolved such an odd shape and whether having eyes so far apart would enhance their vision….

In the second sentence, Barley made it sound like the shark actively evolved its vision for a purpose – a very un-Darwinian notion.  Her choice of title suggests the explanation is, instead, Kiplingian: “Why the hammerhead shark got its hammer.”
    On a related subject, New Scientist and the BBC News reported on research by marine ecologist Andrea Marshall, “queen of the manta rays.”  The shark relatives she studies enjoy a remarkable mutualistic symbiosis with other fish that groom and clean them in “beauty parlors”.  Marshall told New Scientist,

Cleaning stations are pretty well known in the marine environment, but for manta rays it’s an extraordinary event.  Because they are so large, “cleaner fish” partition up the ray and clean different parts of the animal.  It looks so co-operative and gentlemanly.  The mantas have to eat 14 per cent of their body weight a week in plankton, so any time taken out from feeding has to be invested in something important.  As they can spend up to 8 hours having parasites removed and shark bite marks cleaned, it must be detrimental if they’re not groomed.

Evolution was only mentioned briefly in the BBC article to say that a “vestigial sting” in the manta suggests it evolved from the sting ray.  Both articles contain video clips of manta rays in action.  In the New Scientist clip, Marshall said that when she saw one of the giant rays swim over her head in the waters off Mozambique, she was “awestruck by its beauty.” 

Who gave hammerheads 360-degree stereo vision?  Did they think it up on their own and “evolve” their heads and eyes on purpose?  That would be oxymoronic.  There’s nothing evolutionary about this.  In the manta ray “beauty parlors” we see cooperation among creatures – not competition and survival of the fittest.  The cleaner fish act like mechanics on fighter jets that keep the craft in good repair while earning gainful employment.
    Whether or not mantas have vestigial stingers should be critiqued.  If so, it might only suggest a divergence within the ray “kind” (baramin) that represents devolution, not evolution.  Design scientists would approach the structure to see if it has a function.  That approach has many times proved more fruitful than the vestigial organ story (08/21/2009).
    Evolution itself is a vestigial organ of explanation.  It will vanish by intelligently designed thought processes.  We should focus instead on the design of these creatures and enjoy learning more about them.  Proper thinking will result in awe.

(Visited 156 times, 1 visits today)

Leave a Reply