[ravi-delia]

On that last note, a similar thing happens with trees. Trees aren't really a distinct class of organism. The last common ancestor of some trees wasn't a tree, and the last common ancestor of some non-trees was a tree. As it turns out, with a few genetic tweaks lots of plants will slow their metabolic processes and construct a sturdy wood stem, and visa-versa.

Even cooler, perhaps, are eyeless cave fish redeveloping eyes quite quickly after a few generations in the light. It seems like a lot of things are like that. When we look at the fossil record it looks like things evolve in leaps and bounds rather than more gradually over time. Maybe that's because organisms are more built with prefabs rather than from scratch.