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( Toba catastrophe theory)
According to the Toba catastrophe theory, 70,000 to 75,000 years ago a supervolcanic event at Lake Toba, on Sumatra, reduced the world's human population to 10,000 or even a mere 1,000 breeding pairs, creating a bottleneck in human evolution. The theory was proposed in 1998 by Stanley H. Ambrose of the University of Illinois at Urbana-Champaign.[1][2] 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 species, including H. ergaster, H. erectus, H. neanderthalensis and possibly H. floresiensis. According to the Toba catastrophe theory, the consequences of a massive volcanic eruption severely reduced the human population. This may have occurred around 70,000–75,000 years ago when the Toba caldera in Indonesia underwent an eruption of category 8 (or "mega-colossal") on the Volcanic Explosivity Index. This released energy equivalent to about 1&_160;gigaton of TNT (4.2&_160;EJ), fifty times greater than the 1980 eruption of Mount St. Helens[citation needed], and twenty times greater than the largest man-made explosion, the October 30, 1961 detonation of the Soviet Union's Tsar Bomba thermonuclear device. According to Ambrose, the Toba explosion reduced the average global temperature by 5 degrees Celsius (9 degrees Fahrenheit) for several years and may have triggered an ice age. Ambrose proposes that this massive environmental change created population bottlenecks in the species that existed at the time; this in turn accelerated differentiation of the isolated human populations, eventually leading to the extinction of all the other human species except for the two branches that became Neanderthals (H. neanderthalensis) and modern humans (H. sapiens).
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