moe, isn't it highly interesting that life, with the exception of insects and bacteria/viruses (if viruses are indeed life) have two eyes, two ears, 4 limbs, 5 digits on each appendage with a 'claw' on each, and an extremley similair skeletal structure, skull, backbone, ribs, pelvis, etc. Also, humans have a quadraped spine, that's why it's on our back. An ideal biped spine would be in the center of our bodies, supporting our necks and upper body much better and allowing much greater flexability and protecting the highly vulnerable spine better. If you look at the greater picture, mammals are a dominant lifeform because the earth's temperature is no longer a constant sunny place. (palm trees in the north pole) Dinosaurs were at one time dominant proably because as reptiles, they didn't need to generate their own body heat. In fact, reptiles are much more effecient at using energy from food to nurture their bodies. Being a mammal is wasteful, we waste a huge percentage of our food energy for generating heat. Once the earth became cold and had winters, the dinosaurs likley died off because of this, leaving the small mammals who could generate heat as the dominant species. Small rodents and the like.
We have a tail bone, but no tail anymore. Our DNA contains remnats of code once used when we were something else, but now useless. With such similair charactaristsics among mammals and fish and other life, it's not that far of a stretch to go from fish to mammal. Mammals became 'fish' didnt they. Look at the remarkable giraffe. It was once short-necked, and now its got a big-ass neck complete with specialized blood pumping system to help blood reach it's brain just so it can eat some leaves. Or turtles. Evolution does remarkable things.
Look at australia, a continent isolated from the rest of the world's evolutionary process. They have marsupial koalas, and kangaroos. Vastly different animals, yet related by a common ancestor marsupial. Look at the frigin' duck billed platypus! What a freak. It evolved a body similair to a beaver to aid it in water, and also a bill like a duck to aid it in eating the same sort of foods ducks eat. He even lays eggs! That's unheard of in mammals. Clearly, life when left alone for a long long time, will evolve and diverge from common ansestors.
-Dan