Chapter 18.4, Problem 1CSC

Can ancient DNA reveal the secrets of dinosaur evolutionary history? Sadly, no. DNA decays far too quickly to be present in fossils as old as dinosaur fossils are. But all is not lost; the paleontologist Mary Schweitzer and her colleagues have discovered, in some exceptionally well preserved dinosaur fossils, what appear to be preserved soft tissues, such as blood, bone marrow, and skin. These discoveries were initially met with great skepticism that soft tissues could be preserved for so long, but as additional evidence has accumulated, an increasing number of paleontologists have accepted the discoveries. Researchers have extracted proteins such as hemoglobin, keratin, and collagen from the fossil tissue, and the amino acid sequences of these proteins may reveal previously unknown information about the evolution of dinosaurs. Nonetheless, evolution’s historians must, for the most part, rely on more traditional methods. What have such methods revealed about the dinosaur’s successors as Earth’s dominant large animals, the mammals?