April 30, 2010 | David F. Coppedge

Scientist Sees Evolutionary Sense in Coordinated Complexity

An article on PhysOrg tells “A vertebrate story,” and a story it is: the more complex a phenomenon becomes, the more it makes evolutionary sense.
    Portuguese scientists were studying the interaction of Hox genes with the development of the ribs in vertebrates.  You can imagine the control that these genes must have when thinking about the differences between a mouse, with 12 pair of ribs, and a snake, with 200 to 400 pair.  The variety of ribs between a snake and a Tyrannosaurus are staggering, yet are under the control of developmental genes that direct their formation at the right time and place in the embryo.  The genes must be switched on and off in a coordinated fashion for the skeleton to come out right.  It usually does – except when scientists interfere.
    The scientists found that genes for Hox10 are not the only ones involved.  Another class, called Hox6, interacts with Hox10 to regulate the formation of vertebrae.  By deactivating these genes they could get embryos to grow extra ribs in different portions of the spine.  They found that one set of genes promotes rib formation in the thoracic region, while another blocks the activity in the lumbar region.  Then they found that the genes for rib formation do not switch on unless genes that control the formation of both muscles and ribs are also switched on.  Suddenly the picture started looking a lot more complicated.
    One would think this complexity would create additional problems for evolutionary theory.  Moises Mallo, however, waltzed right past the problem and rejoiced in the new insights it provided him.  Here is his prize for Stupid Evolution Quote of the Week: “Our findings reveal a more complicated process than we would have imagined, but one that makes perfect sense, from a functional and evolutionary point of view: it is no good to make ribs without muscle, so, in the embryo, the production of both ribs and their associated muscles is under the control of a single and coordinated mechanism.”

You may now all emit a collective groan.  Make sure it is heard at the Instituto Gulbenkian de Ciencia, where certain people need to be turned right-side up.  Evolutionary sense: how’s that for a prize-winning oxymoron?  David Berlinski put it well: “The unfathomable complexity of living systems, Darwin’s theory affirms, is the result of random variation and natural selection.  Is it indeed?  Of these concepts, the second is hopelessly confused and the first is of no intellectual interest” (Daily Californian, 04/01/2005).  No wonder he began that essay with the line, “Wearing pink tasseled slippers and conical hats covered in polka dots, Darwinian biologists are persuaded that a plot is afoot to make them look silly.”  That’s about all they’re wearing, too.

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