An interesting article in this week's edition of Nature suggests that at least in some fish, alterations in a single gene bring about evolutionary change in the form of limb (fin) loss.
Genetic and developmental basis of evolutionary pelvic reduction in threespine sticklebacks
MICHAEL D. SHAPIRO, MELISSA E. MARKS, CATHERINE L. PEICHEL, BENJAMIN K. BLACKMAN, KIRSTEN S. NERENG, BJARNI JÓNSSON, DOLPH SCHLUTER & DAVID M. KINGSLEY
Nature 428, 717–723
Eurekalert press release
Original Article
Discussion by Shubin & Dahn
2 Comments
Loren Petrich · 14 April 2004
Interesting. And this sort of change is another way that evolution can happen in bursts. Goldschmidt's "Hopeful Monsters" have been much ridiculed, with some justification, but the growth of evolutionary developmental biology has enabled hypotheses like these to become testable.
Now to snakes. As I understand it, snakes do not grow front limbs because they no longer have a front-limb Hox zone; they have no place where the expression and non-expression of various Hox genes will induce the growth of front limbs. By comparison, their hindlimbs buds grow and then get resorbed in completely-legless snakes.
But in limb evolution, it is difficult to compete with arthropods -- a single individual one can have limbs specialized in several different ways.
Sarah Sterling · 6 November 2004
Ciao