he Cambrian explosion describes the appearance of thousands of new species about 542 million years ago. Greater competition among species following the Cambrian explosion led to more rapid adaptation. Certain adaptations led to the origin of amphibians that brought life onto land. A meteorite impacts the dominant species. At about 65 million years ago, a carbonaceous meteorite impacted Earth, blocking out the Sun, and causing plants to die and temperatures to drop. This impact led to the extinction of many species, as well as the dinosaurs. As Earth recovered from the impact, mammals were able to take over. In the Tertiary period, the diversity of mammal species grew as the group proliferated. However, in the late Pleistocene, the earliest part of the Quaternary period, the larger mammal species, such as mammoths and mastodons became extinct. At the beginning of the Quaternary period, the first humans began to evolve. Conditions on Earth influenced evolution and how biodiver