According to the Toba catastrophe theory, modern human evolution was affected by a large volcanic event.⁠ Within the last three to five million years, after human and other ape lineages diverged from the hominid stem-line, the human line produced a variety of human species.⁠ According to the Toba catastrophe theory, a massive volcanic eruption changed the course of human history by severely reducing the human population.⁠ This occurred when, around 70–75,000 years ago, the Toba caldera in Indonesia underwent a category 8 or "mega-colossal" eruption on the Volcanic Explosivity Index.⁠ ⁠ _____⁠ ⁠ This has reduced the average global temperature by 3 to 3.5 degrees Celsius for several years and may have triggered an ice age.⁠ This massive environmental change is believed to have created population bottlenecks (a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities) in the various spec...