crashfrog writes:
We don't see those hard spots in
living creatures now because that evolution
already happened. Organisms already have skeletons. Why would they evolve again?
eek, that's a clearly false notion of evolution. evolution is
not directed, nor does it forbid convergence, nor does it necessitate that once an adaptation is successful that it be adopted across lineages -- no, it actually predicts that won't happen. that would be a good sign of intelligent design.
in any case, here are some
living animals with various states of "hard spots" on the way to having a bony skeleton.
amphioxus, somewhat basal chordate. spinal column, somewhat rigid.
lamprey, jawless fish. cartilaginous skeleton, no bones.
shark, jawed fish. bony jaw, cartilaginous skeleton.
these are, of course, somewhat representative of the fossil record.
אָרַח