The Sixth Extinction D id you know that most of the species that have ever lived on Earth are now extinct Did you know that the majority of life on Earth has never been known to us Every day many species of animals perhaps hundreds become extinct without us even knowing they existed Throughout the Earth’s history species have become extinct due to natural causes Scientists recognize that there have been five mass extinctions caused by astronomical geological or volcanic events Each of these extinctions wiped out between 50 and 95 percent of the wildlife of the time The most recent of these was about 65 million years ago when a giant asteroid is thought to have collided with the Earth This brought about the extinction of three quarters of the Earth’s animal species including the dinosaurs After a mass extinction like this it takes at least 10 million years for the biological diversity to recover Ammonites were marine mollusks that lived hundreds of millions of years ago They became extinct at the same time as the dinosaurs about 65 million years ago Their fossilized remains are found throughout the world 4
Today we are living in the middle of a sixth great extinction Unlike the others this one has a different cause human activity It probably began 50,000 years ago when early humans started to migrate around the world and began hunting with Stone Age weapons Since the 1600s more than 250 large animal species became extinct every one caused by humans Over 16,000 more are threatened with extinction This loss is due to the damage and pollution of the environment loss of habitats overhunting agriculture and the introduction of alien species Once an animal species is extinct it is gone forever We need to act now to conserve the amazing biodiversity on our planet and to ensure it will be there for future generations In the Americas the hunting activities of early humans eventually caused a continent-wide extinction of animals such as saber-toothed cats wild horses and ground sloths a fossilized skeleton of which is seen here HOT SPOT Last One Left George the tortoise below is the very last of a species of Galapagos island giant tortoise He lives on the island of Pinta and has been in captivity for 36 years He is literally the rarest animal in the world 5
