January 18, 2008 | David F. Coppedge

Mouse Grows Long Finger, Takes Off Like a Bat

When does humor in a scientific journal cross the line of scientific objectivity?  You be the judge.  Science magazine, in its “Random Samples” news featurette, said this in the Jan. 18 issue:

Over the past 100 million years or so, bats have evolved many features that distinguish them from their mammalian cousins.  One is long, bony digits to support their wings.  Now, by manipulating one small DNA sequence, Richard Behringer of the University of Texas M. D. Anderson Cancer Center in Houston and colleagues have nudged mice a tiny step along the evolutionary path to bat-hood.
    The researchers looked at the expression of a homeobox gene, prx1, a key to the development of limbs in all mammals, and found that bats expressed the gene differently from mice in embryonic limbs.  So, in mice they removed a chunk of DNA known to control prx1 expression and replaced it with the same piece from bats.  The forelimbs of the resulting mice were 6% longer than those of normal baby mice.  Although small, that increase is “important,” says developmental biologist Clifford Tabin of Harvard Medical School in Boston.
    Similar studies have been done with flies and worms, but this is the first to show how a specific change in control of gene expression–and not an actual gene–can produce a gross morphological change in a mammal, says Behringer, whose study was published this week in Genes & Development.  “If you play this through with lots and lots of genes, maybe ultimately we could make that mouse fly out of the cage.”

Bats, of course, have sophisticated flying skills, membranes for lift, specialized ears and mouth parts for sonar (with a brain to use them), special feet for clinging to cave roofs, dietary adaptations, and “many features that distinguish them from their mammalian cousins.”  The earliest known fossil bats already had these adaptations (05/18/2007), and their evolutionary history is “largely unknown” and their fossil record “impoverished” (01/28/2005).  It would seem much more than adding a millimeter or so to the forelimbs would be necessary before the mouse could fly out of the cage.

OK, so the cute extrapolation was meant to be a little extreme for humor.  We try to have fun in our reporting, too.  What’s not funny is that in reality, they are dead serious.  They really believe a 6% change in a finger length is actually a “step along the evolutionary path to bat-hood.”  Give it 100 million years and these small changes can add up to major transformations.  And you thought orthogenesis went out in the 1920s.
    Too bad we already awarded SEQOTW this week.  This would have been a good one: evolutionists take giant leap on the path to batty-hood.

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Categories: Dumb Ideas, Genetics, Mammals

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