Over the course of Earth's history, there have been five mass extinction events, each wiping out a significant proportion of the planet's species. The first, known as the Late Ordovician Extinction, occurred approximately 444 million years ago and was caused by a combination of factors including a sudden drop in sea levels and a global cooling event. The second, the Late Devonian Extinction, took place about 360 million years ago and is thought to have been triggered by climate change and volcanic eruptions. The third, the Permian-Triassic Extinction, was the most severe of all, wiping out nearly 90% of marine species and 70% of terrestrial vertebrates around 252 million years ago, potentially caused by a combination of asteroid impact, volcanic activity, and global warming. The fourth, the Late Triassic Extinction, occurred 201 million years ago and is believed to have been caused by volcanic eruptions and climate change. The fifth and most recent, the Cretaceous-Paleogene Extinction, took place 66 million years ago and is widely attributed to the impact of a large asteroid or comet. These mass extinction events have had profound impacts on the evolution of life on Earth, shaping the diversity of species and ecosystems that exist today.
