Five mass extinction events have swept Earth, each wiping out most species — and many biologists argue the sixth is already in its early stages, driven not by an asteroid or volcanic eruption but by a single species altering the atmosphere, oceans and ecosystems faster than many other species can adapt or move

That speed is at the center of one of the most troubling debates in modern biology: another mass extinction may already be beginning. What counts as a mass extinction, and why fiveThe phrase “mass extinction” gets used loosely, but paleontologists have a fairly specific meaning in mind. How the sixth is different: no asteroid, no supervolcano, just usThe idea that humans might be causing a sixth mass extinction became widely known through Richard Leakey and Roger Lewin’s 1995 book and, later, Elizabeth Kolbert’s Pulitzer-winning The Sixth Extinction. They write: “Beyond any doubt, the human-driven sixth mass extinction is more severe than previously assessed and is rapidly accelerating.” Our read is that the sixth mass extinction is not yet a finished fact.