About 98% of the organisms that ever existed on our planet are now extinct. Mass extinctions refer to the loss of 75% of species over a short geological time period, which can be up to 2.8 million years. There have been five since the start of life on Earth. However, comparative to previous mass extinction events caused by asteroids or the end of the ice age, this sixth mass extinction is the work of humankind. Research suggests that without human interference, species that have already perished could have persisted for another 800 to 10,000 years. This mass extinction event is occurring at an accelerated rate to any one preceding it.