January 29, 2011 | David F. Coppedge

Fishy Just-So Stories

“How the Seahorse Might Have Got Its Shape” (italics added) is a backpedal on the Just-So Story formula (e.g., “How the Zebra Got Its Stripes,” Kipling).  Was the evolutionist hedging his bets this time?  PhysOrg continued the possibility thinking with its subtitle, “The shape of the seahorse has long baffled marine scientists, but new research suggests the seahorse’s unique shape may have evolved to allow it to catch its food when it was further away.”  May have, might have; that’s the power of suggestion.  The BBC News, however, threw caution to the waves and declared that the seahorse’s body shape has been “explained”.
    The storyteller is a Belgian scientist, Sam Van Wassenbergh (U of Antwerp).  He compared seahorses with their relatives, the pipefish, which lack the characteristic curvature that makes seahorses distinctive in their upright swimming position.  He found that the curvature helps the seahorse, a weak swimmer, increase its striking range to catch prey.  A video clip explains the theory, followed by this paragraph at the end of the PhysOrg article:

Dr Van Wassenbergh said the foraging behavior would have come first and then natural selection would favor those fish that had a larger strike distance.  According to their research this created a selective pressure for the angle between head and trunk to increase.

The video clip was less bashful about the Just-So Story, ending, “…and that’s how the seahorse got its shape.”
    What Wassenbergh didn’t explain, though, was why pipefish didn’t follow suit, if this is such a good strategy for natural selection to work on.  In fact, the pipefish and seahorses seem to live in the same environments and do equally well at feeding and surviving.  It would seem an equally good story could be told about “How the Pipefish Got its Shape” – how selection pressure straightened out the weak-swimming, ungainly seahorse so that it could approach its prey with more speed.  Perhaps a more scientific title, then would be, “Why the Seahorse Has Its Shape,” not how it got its shape.  Then it becomes a story about biophysics, not evolution.
    A slightly stranger story on PhysOrg proposed that angelfish can do math.  When joining a group, or shoal, they appear to always prefer a shoal size with a ratio of 1.8 over another.  The article hedged its bets on what this might mean about angelfish brains and abilities, and even whether the observations hold true under other circumstances.  This second article did not mention evolution.

What’s the matter with the angelfish researchers?  They didn’t do their job.  They didn’t tell a story about how evolution accounted for the angelfish’s mathematical mind.
    The first one did it right.  Natural selection made pipefish straight, and it made seahorses curved.  This is known as scientific explanation.  Opposite outcomes occur from the same law of nature, the law of natural selection (12/19/2007).  These opposite outcomes can be subsumed under the Stuff Happens Law, which explains everything (see 09/15/2008 commentary for why this law is scientific).
    To exercise scientific restraint, you can say Stuff Might Happen; then when it does, you are acclaimed as The Scientist – a Priest of sorts, mediating between the mysterious workings of the cosmos and the peasants, providing them the comfort and assurance that comes with understanding.  Assume the lotus position and recite the mantra Stuffffff Happpppennnnnzzzzz till a state of nothingness descends upon you.  You have arrived at Niwrada (01/26/2010 commentary).

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