Toba disaster theory

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Coordinates: 2 ° 36 '  N , 98 ° 49'  E

False-color satellite image of Lake Toba , the 100 km long and 30 km wide caldera of a super volcano

According to the Toba catastrophe theory , human expansion was strongly influenced by the massive volcanic eruption of Toba ( Sumatra ), which occurred 73,880 ± 320 cal BP years ago. The theory was proposed by Stanley H. Ambrose in 1998 .

Theory

Ambrose's theory states that as a result of a massive eruption (category 8 on the volcanic explosion index ), the human population on earth at that time was greatly reduced. In the following years, the eruption led to a drop in average temperature of 3 to 3.5 degrees Celsius , and according to a model calculation published in 2009, possibly even to an even greater drop in temperature. This thesis of a short global ice age is supported by the dating of the last glacial period (known as the Würm glacial period in southern Germany and the Vistula glacial period in northern Germany ).

The last glacial period , shown in the ice core data from Antarctica and Greenland

The Toba catastrophe theory itself may also be supported by Greenland ice cores obtained from the Greenland Ice Core Project and the Greenland Ice Sheet Project , which show a massive disruption in ice build-up about 71,000 years ago. However, this was not observed in the Antarctic ice. Critics point out that the Toba volcanic eruption did not release enough sulfur into the atmosphere to cause global cooling - instead, a large amount of rock was thrown up. The eruption had an energy of about one gigatonne TNT equivalent . The Indian subcontinent was covered with an approximately 15 cm thick layer of ash. Archaeological digs in India uncovered similar stone tools above and below this layer, suggesting that the Homo erectus population in India survived the Toba disaster.

An average global cooling does not have to have occurred globally uniformly and briefly (as in the volcanic winter - compare year without summer after the Tambora event), it could also have been hit by an ice age tendency and, due to massive climate change, some (regionally proven) decades of cold periods caused (compare small ice age ).

Human population bottleneck

About 7 million years ago the line of development of the hominini leading to modern humans (Homo sapiens) separated from that of the chimpanzees . After numerous intermediate stages, called Chronospecies , Homo erectus finally gave rise to both the Neanderthals (Homo neanderthalensis) and Homo sapiens and probably Homo floresiensis . At the time of the Toba eruption, Homo sapiens existed in Africa , Neanderthals in Europe, and Homo erectus and Homo floresiensis in Asia .

The Toba catastrophe theory claims to provide an explanation for the close genetic relationship of all humanity today. Calculations on the mutation rate of the human genome (see mitochondrial Eve and especially Adam of the Y chromosome ) have shown that around the time of the Toba explosion there could have been a so-called genetic bottleneck in humans , i.e. a reduction in size of Homo sapiens, who then lived in Africa - Population to a few thousand individuals. However, these genetic calculations have so far not been supported by archaeological or paleoanthropological finds. Direct effects on the Neanderthals and on animal and plant species are also so far unknown.

According to the Toba catastrophe theory, Asia and Europe, based on the small African population of Homo sapiens , were colonized by the latter after the Toba catastrophe. The species of the genus Homo, which were previously resident in Asia and Europe , then became extinct within a few thousand years. The theory thus also claims to provide an ecological explanation for the Out-of-Africa theory , which is well supported by numerous fossil finds .

criticism

The Toba catastrophe theory is controversial among paleoanthropologists because the stone tools that have been recovered since 2003 in southern India near Jwalapuram , in the valley of the Jurreru River, suggest a continuous history of settlement for this region. These stone tools were discovered directly below and directly above the Toba tuff layers and show a continuity in appearance and manufacturing technique , because they are less similar to the stone tools made in Levallois technique from other Asian sites (which come from Homo erectus in Asia and from Neanderthals in Europe ); Rather, they are similar to the stone tools known from the African Homo sapiens of this era. The assignment of these finds to Homo sapiens was questioned in 2013 with reference to genetic and archaeological findings, but stone tools from a second site in northern India were assessed in 2020 as confirmation of the continuous settlement of the region by Homo sapiens . Excavations at other Indian sites also confirmed the continuity of settlement in India.

But if groups of the genus Homo survived the Toba catastrophe in relatively close India, why should they have come close to extinction in far-away Africa ?, was asked in the journal Science in 2010 . The fossils of Homo floresiensis discovered in 2003 on the nearby island of Flores and stone tools found in the Soa basin are interpreted as evidence of a continuous history of settlement by groups of the genus Homo on Flores. A detailed analysis of the sediments in Lake Malawi , 7000 kilometers west of Toba, also did not reveal any evidence of dramatic changes in temperature or in the composition of the algae species below and above the ash layers, which are also detectable in East Africa ; the Toba eruption could therefore not be seen as the cause of a “genetic bottleneck” in East Africa.

Another possibility to investigate the effects of the Toba eruption on the populations of Homo sapiens living in Africa was offered by the reliably reconstructable legacies of the Pinnacle Point people and the stratification of an excavation site around nine kilometers from them near the Vleesbaai community in South Africa . According to a study published in Nature in 2018, pyroclastic sediment was identified at both locations , the chemical properties of which correspond to samples from Malaysia and Lake Malawi of the same age and which can therefore be assigned to the Toba eruption. When comparing the layers immediately above the Toba tracks with those immediately below the Toba tracks, the researchers found no evidence of an interruption in the use of both excavation sites. On the contrary, according to the researchers , the evidence of a colonization by Homo sapiens increased shortly after the Toba eruption: "We found no evidence that the Toba outbreak had any influence on people's daily lives."

Europe: the thicker glaciations of the penultimate glacial period compared to those of the last glacial period.

According to some researchers, the possible cause of the “genetic bottleneck” is not the last but rather the penultimate glacial period, which began 195,000 years ago and ended approximately 123,000 years ago. It is referred to as the geological stage oxygen isotope level 6 (MIS 6). “Previously there were always more than 10,000 adults of reproductive age, but now it is unlikely to have been a few hundred. […] At that time, the continent had only a few areas that had sufficient resources for hunters and gatherers. ”In Northern Europe, this glacial period corresponds to part of the Saale complex , in the Alpine region the Riss glaciation .

literature

  • Clive Oppenheimer: Eruptions that Shook the World . Cambridge University Press, 2011, ISBN 978-0521641128

See also

Web links

Individual evidence

  1. ↑ Michael Storey et al .: Astronomically calibrated 40Ar / 39Ar age for the Toba supereruption and global synchronization of late Quaternary records . In: PNAS , Volume 109, No. 46, 2012, pp. 18684–18688, doi: 10.1073 / pnas.1208178109
  2. ↑ Stanley H. Ambrose: Late Pleistocene human population bottlenecks, volcanic winter, and differentiation of modern humans . In: Journal of Human Evolution . Volume 34, No. 6, pp. 623-651. doi : 10.1006 / jhev.1998.0219 .
  3. ^ Stanley H. Ambrose: Volcanic Winter, and Differentiation of Modern Humans. In: Bradshaw Foundation. 2005, accessed March 13, 2018 .
  4. ^ A. Robock, CM Ammann, L. Oman, D. Shindell, S. Levis, G. Stenchikov: Did the Toba volcanic eruption of ~ 74k BP produce widespread glaciation? . In: Journal of Geophysical Research . Volume 114, p. D10107. doi : 10.1029 / 2008JD011652 .
  5. ^ Alan Robock et al .: Did the Toba volcanic eruption of ∼74 ka BP produce widespread glaciation? In: Journal of Geophysical Research. Volume 114, No. D10, 2009, doi: 10.1029 / 2008JD011652 , full text (PDF)
  6. ↑ a b https://derstandard.at/1246541616765/Die-groesste-Krise-der-fruehen-Menschheit The greatest crisis of early mankind in Der Standard , Vienna 7 July 2009
  7. ↑ Frederick J. Gathorne-Hardy and William EH Harcourt-Smith: The super-eruption of Toba, did it cause a human bottleneck? In: Journal of Human Evolution. Volume 45, No. 3, 2003, pp. 227-230, doi: 10.1016 / S0047-2484 (03) 00105-2 , full text (PDF) .
    Stanley H. Ambrose: Did the super-eruption of Toba cause a human population bottleneck? Reply to Gathorne-Hardy and Harcourt-Smith. In: Journal of Human Evolution. Volume 45, No. 3, 2003, pp. 231-237, doi: 10.1016 / j.jhevol.2003.08.001 .
  8. ↑ "We provide here firm chronological evidence that hominins were present in the Jurreru River valley, south India, immediately before and after the YTT [Youngest Toba Tuff eruption, which occurred in Indonesia 74,000 years ago] eruption." Michael Petraglia et al .: Middle Paleolithic Assemblages from the Indian Subcontinent Before and After the Toba Super-Eruption. In: Science . Volume 317, 2007, pp. 114-116, doi: 10.1126 / science.1141564 .
  9. ↑ Paul Mellars et al .: Genetic and archaeological perspectives on the modern initial human colonization of southern Asia. In: PNAS. Volume 110, No. 26, 2013, pp. 10699-10704, doi: 10.1073 / pnas.1306043110 .
  10. ↑ Chris Clarkson: Human occupation of northern India spans the Toba super-eruption ~ 74,000 years ago. In: Nature Communications. Volume 11, Article No. 961, 2020, doi: 10.1038 / s41467-020-14668-4 .
  11. ^ Michael Balter: New work may complicate history of Neandertals and H. sapiens. In: Science , Volume 326, 2009, pp. 224-225, doi: 10.1126 / science.326_224 .
  12. ^ "If modern humans survived there relatively unscathed, African populations would likely have fared even better." Michael Balter: Of two minds about Toba's impact. In: Science. Volume 327, 2010, pp. 1187-1188, doi: 10.1126 / science.327.5970.1187-a .
  13. ↑ Christine S. Lane et al .: Ash from the Toba supereruption in Lake Malawi shows no volcanic winter in East Africa at 75 ka. In: PNAS . Volume 110, No. 20, 2013, pp. 8025-8029, doi: 10.1073 / pnas.1301474110 .
  14. ↑ Chad L. Yost, Lily J. Jackson, Jeffery R. Stone, Andrew S. Cohen: Subdecadal phytolith and charcoal records from Lake Malawi, East Africa imply minimal effects on human evolution from the 74 ka Toba supereruption. In: Journal of Human Evolution. Volume 116, 2018, pp. 75-94, doi: 10.1016 / j.jhevol.2017.11.005 .
  15. ^ Eugene I. Smith et al .: Humans thrived in South Africa through the Toba eruption about 74,000 years ago. In: Nature. Volume 555, 2018, pp. 511-515, doi: 10.1038 / nature25967
  16. ↑ How ancient humans survived global 'volcanic winter' from massive eruption. On: sciencemag.org from March 12, 2018
  17. ↑ The little Gallic village. On: wienerzeitung.at from March 12, 2018.
  18. ↑ Curtis W. Marean: When humans nearly died out . In Spektrum der Wissenschaft , No. 12/2010, pp. 58–65