
You can say this about mammals: We've had a good run.
Over the 250 million years since the first mammals diverged from reptiles and birds, we hairy, warm-blooded vertebrates have come to dominate the Earth, with rodents and humans and ungulates and whales living on nearly every inch of the planet.
But the end to that reign may come much sooner than traditionally thought, suggests a new study published this week in the journal Nature Geoscience.
Scientists have long thought that life on Earth will continue until the planet enters its "runaway greenhouse" phase — a state in which water vapor and other greenhouse gasses in the atmosphere become so dense that heat can't escape the surface and the oceans boil away, like the planet Venus. That's 2 or 3 billion years away.