Extinction happens when a animal Specie dies and is wiped out of there environment damagin the Food Chain and life on the planet. The Dinosaurs where wiped out because of reason that is not now but the Scientist believed that Dinosaurs and many animal Species were killed by a meteor that landed on todays Yucatan,Mexico.There are no know Species to come back to life after Extinction.Some Scientist believed that if Dinosaurs dint die Human Race woud had not exist.If Dinosaurs came back to life they coud damage the Food Chain if we let them out like normal animals.