| Scientists have concrete evidence that the Earth is | | | | years ago. |
| currently undergoing the largest mass extinction in 65 | | | | Was it caused by climate change, asteroids, or |
| million years. Over 50 species are going extinct every | | | | volcanoes? The verdict isn't clear. What is clear is that |
| single day. | | | | 20% of marine life and many large amphibians were |
| It's called the Holocene Extinction - Holocene being the | | | | wiped out. At least half of all species on the planet bit |
| current epoch that began at the end of the last ice | | | | the dust. |
| age, about 10,000 years ago. | | | | This event occurred over less than a 10,000 year |
| From Earth's fossil record, we know about Six Great | | | | period, just before the supercontinent of Pangea |
| Mass Extinctions: | | | | began to break up. |
| The Ordovician-Silurian Extinction occurred about 444 | | | | The Cretaceous-Tertiary Extinction occurred about 65 |
| million years ago. | | | | million years ago. |
| At the time, all complex organisms lived in the sea. The | | | | This event was probably caused, or at the least |
| most common theory is that the onset of an ice age | | | | aggravated by, the impact of an asteroid around the |
| caused the extinction, which wiped out over 100 | | | | size of Manhattan. About 16% of marine families and |
| families of marine life. Many trilobite families bit the dust | | | | 18% of land vertebrate families ceased to exist. In |
| during this event. | | | | North America, over 50% of plant species may have |
| The Late Devonian Extinction happened 364 million | | | | been wiped out. |
| years ago. | | | | And of course...this is the event that doomed the |
| This event saw a major worldwide extinction of coral | | | | dinosaurs. |
| reefs and the marine life they supported, as well as | | | | The Holocene Extinction is occurring now. |
| other groups of animals and plants. Nobody's sure | | | | Studies of the fossil record show that the normal |
| what caused it, but scientists speculate global cooling | | | | "background" rate of extinction is about one species |
| and several medium-sized asteroid impacts within a | | | | every four years. The current rate is between 30,000 |
| few million years of each other may have been the | | | | and 100,000 per year. |
| culprits. | | | | You are now witnessing the fastest of the six great |
| The Permo-Triassic Extinction occurred 251 million | | | | mass extinctions. |
| years ago. | | | | And this extinction, without a doubt, is the result of |
| The granddaddy of all mass extinctions, this event | | | | human population growth. By the end of this century, |
| saw 96% of all marine species and 70% of land | | | | over five million species (half of the species on Earth |
| vertebrate species kick the evolutionary bucket. | | | | now) will likely be gone. |
| The die off happened in less than a million years (a | | | | "It's not just species on islands or in rain forests or just |
| very short time in geological terms) and the recovery | | | | birds or big charismatic mammals," says Stuart Pimm, |
| took 5 million years to crank back up, and another | | | | a conservation biologist researcher from the University |
| million years after that to get rolling. While not deemed | | | | of Tennessee. He notes fish, birds, insects, plants, and |
| the smoking gun yet, this event coincides with the | | | | mammals. "It's everything and it's everywhere...it is a |
| largest known volcanic eruption in history. | | | | worldwide epidemic of extinctions. |
| The Triassic-Jurassic Extinction occurred 200 million | | | | |