Many Paleontologists used to believe that birds evolved in a straight line from dinosaurs, in much the same way it is believed humans evolved from a common ape ancestor. Challenging evidence now demonstrates that birds have a common ancestor shared with dinosaurs, but the two species evolved apart from each other, which is a bit mind blowing. I was already blown away by the fact that a large 25 foot mammal very much related to cows and other bovine creatures returned to the sea and became the ancestor of all cetaceans (dolphins, whales, narwhals, etc.). Hey, the same thing could happen to our species in a million years. Ever read Galapagos?