Transmutation on Tuesday

Wherein we talk evolution, or cases thereof.

A new paper from Stuart Newman, a development biologist at New York Medical College, is generating some heat in an already torrid arena - the one that looks at the evolution of birds and of flight.  The most notable features of birds, of course, are feathers and wings and the flight that they allow.  Not far behind, though, is the prodigious musculature that drives those wings.  In some birds, the pectoral muscles alone make up 20% of the mass of the animal. 

This seems simple enough to explain.  Flight isn't easy.  I routinely offer a free A to any of my vertebrate zoology students who can open the second floor windows of Bibb Graves Hall and take off.  No one's claimed it yet.  On the surface it seems clear that, as birds developed flight, they gradually developed the powerful musculature to drive it.

Newman has another idea, and it's related to genetics (as, it seems, everything is these days).  It appears that the dinosaur ancestors of birds lost the gene to produce uncoupling protein-1 (UCP1).  This gene is required  for the ability of "brown fat" tissue to generate heat.  In newborn mammals, it is the heat generated by this tissue that provides protection from hypothermia.    Newman suggests that, following the loss of this gene, the ancestors of birds had to rely on increased muscle mass to generate the needed heat.  He thinks that this increased muscle mass enabled them to move to an upright, bipedal posture.  And, he further believes, it was this upright posture that enabled the anterior appendages to be modified for extravagances like flight.