More than 100 million years ago, scientists say, warming seas and reduced oxygen may have sent some sharks higher into the water column, where they evolved to be fierce and hungry. More than 100 million years ago, scientists say, warming seas and reduced oxygen may have sent some sharks higher into the water column, where they evolved to be fierce and hungry. Sharks, Fossils, Paleontology, Endangered and Extinct Species, Research, Global Warming, Current Biology (Journal), your-feed-science, your-feed-animals NYT > Science