<< This is hardly a problem, and it is certainly not an "intractable" one. It
is predicted (more or less uniquely) on the basis of the very principle of
evolution that organisms will increase in complexity to fill every available
niche, as long as each increase in complexity also brings with it a survival
advantage for the genes of the organism. Indeed, that's pretty much the
*point* of evolutionary theory.>>
Someone needs to explain this to bacteria. They are the predominate
life form on earth and have been evolving for the longest period of time.
Yet there is no clear trend that bacteria have increased their complexity
to fill every available niche.