Fossils challenge DNA in the dating game

摘要

Yet again, molecules and fossils are at odds in the dating of a key event in the history of life. On page 1003 of this issue, palaeontologist John Wible of the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, and his colleagues use their discovery of a Cretaceous mammal from Mongolia to build the most complete fossil-based mammal family tree so far. It suggests that modern mammals arose only after the dinosaurs went extinct 65 million years ago, thus contradicting dates derived from the DNA of living mammals — including another recent Nature paper (O. R. Bininda-Edwards et al. 406, 507-512; 2007). In the DNA analyses, modern groups appear earlier, between 100 and 80 million years ago, with the extinction of the dinosaurs seeming to have had little effect on their evolution.