A team of American and European researchers have confirmed that the CretaceousPaleogene extinction -- the event that wiped out roughly 75% of the planet's species, including almost every dinosaur -- was caused by an asteroid impact in Mexico 66 million years ago. The CretaceousPaleogene extinction was the last great extinction event to occur on Earth, and is most notable for causing the diversification of mammals that eventually resulted in Homo sapiens.