Toba catastrophe theory
According to the Toba catastrophe theory, the propagation of man by the massive volcanic eruption of Toba (Sumatra ), which took place in front of 73,880 ± 320 cal BP years, strongly influenced. The theory was proposed by Stanley H. Ambrose of the University of Illinois at Urbana -Champaign in 1998.
The theory
The theory of Ambrose says that ( on the Vulkanexplosivitätsindex category 8 ), the then human population on Earth has been greatly reduced due to a massive eruption. The eruption resulted in the following years to a decrease in the average temperature by 3 to 3.5 degrees Celsius.
Alan Robock of Rutgers University in New Jersey has calculated even graver consequences in newer computer models. So should initially be decreased by up to 18 degrees, the world's temperatures, and after a decade, the temperature was still located by an average of ten degrees lower. This thesis is a brief global ice age is supported by the dating of the Würmkaltzeit and Weichsel glacial period in Europe.
The Toba catastrophe itself may be also supported by Greenland ice cores that were obtained as part of the Greenland Ice Core Project and the Greenland Ice Sheet Project, and which show a massive disturbance in the build up of ice about 71,000 years ago. In the Antarctic ice which was not observed. Critics point out that the Toba volcanic eruption is not enough sulfur cheered in the atmosphere to cause global cooling. Instead, a lot of rock was thrown up - the outbreak had an explosive force of about a gigaton TNT - was coated in consequence of the Indian subcontinent with an approximately 15 cm thick layer of ash. Here, too, has been criticized because during archaeological excavations in India stone tools have been found from this period, suggesting that the population of Homo erectus survived the Toba catastrophe in India.
A slowdown in global average temperature must therefore occurred not globally uniform and short ( as in volcanic winter - compare year without a summer ), it might be best taken at a glacial trend and have caused massive climate change in some (regional proven ) decades- long cold periods (see little Ice Age ).
Population bottleneck in humans
About 7 million years separated the lineage of modern man (Homo sapiens) leading Hominini from that of chimpanzees. After numerous, Chrono species mentioned intermediates eventually went from Homo erectus both the Neanderthals (Homo neanderthalensis ) and Homo sapiens and Homo floresiensis probably out. At the time of the Toba eruption existed in Africa, Homo sapiens, Neanderthals in Europe and Homo erectus in Asia and Homo floresiensis.
The Toba catastrophe theory purport to provide an explanation for the close genetic relationship of the entire humanity today. Calculations of the rate of mutation of the human genome (see Mitochondrial Eve and especially Adam of the Y chromosome ) have shown that there might have been about the time of the Toba explosion called a genetic bottleneck in humans, ie a reduction of the then living in Africa, Homo sapiens population to a few thousand individuals. However, these genetic calculations have not yet been supported by archaeological or paleoanthropological discoveries. Also a direct impact on Neanderthal and on animal and plant species are unknown.
According to the Toba catastrophe theory to Asia and Europe, starting from the small African population of Homo sapiens, have been colonized by the Toba catastrophe of this. The Asia-based and European species of the genus Homo are then extinct within a few thousand years. The Toba catastrophe theory also rises so that claim to provide an ecological explanation for the well-protected by numerous fossil finds out- of-Africa theory.
Criticism
The Toba catastrophe theory is controversial among paleoanthropologists. In particular, since 2003, in South India at Jwalapuram, in the valley of Jurreru River, recovered stone tools place which was near continuous settlement history of the region. These stone tools were discovered just below and just above the Toba Tuff layers and show a continuity in appearance and production technology, because they resemble less the stone tools of other Asian places of discovery produced in Levallois ( which originate in Asia, Homo erectus and in Europe from Neandertals ); rather, they have a similarity with the known from the African Homo sapiens stone tools of this era. The assignment of the finds to Homo sapiens was, however, contradicted in 2013 with reference to genetic and archaeological findings.
Excavations at other Indian sites confirmed in the following years, at least the continuity of settlement. But if groups of the genus Homo survived the Toba catastrophe in the relatively near India, why should he be then come close to extinction in Africa far away? Also discovered on the nearby island of Flores in 2003, fossils of Homo floresiensis and discovered in the Soa Basin stone tools have been interpreted as evidence for a continuous settlement history of groups of the genus Homo on Flores.
A detailed analysis of sediments in the 7000 km westerly of Toba Lake Malawi was also no evidence of dramatic changes in temperature or the composition of the algal species below and above the detectable also in East Africa ash layers; the Toba eruption can not therefore be regarded as the cause of a " genetic bottleneck" in East Africa.
A possible cause for the " genetic bottleneck" comes after some researchers consider especially a cold period in question, which began 195,000 years ago and ended about 123,000 years; it is as a geological stage oxygen - isotope stage 6 (MIS 6 ) refers to: " Lived previously always well over 10,000 adults of reproductive age, so it should now be hardly been a few hundred. [ ... ] The continent had at that time only a few areas, which kept ready for hunting and gathering enough resources. "