National Geographic: More than 400 million years ago, Earth’s dramatically warmer sea temperatures plummeted to almost present-day levels, opening the door for a boom in biodiversity, new research shows. The cooler seas–which occurred during the Ordovician period–created a more hospitable environment for a range of species, researchers say. The find might also foreshadow a biodiversity crisis if the planet continues to warm due to climate change. “It’s a warning of what happens to life …